How to Calculate Monthly IO Home Loan Payments (2023)

Calculate Your Monthly Mortgage Payments

How to Calculate Monthly IO Home Loan Payments (2)

The first calculator is a basic tool which shows monthly principal and interest payments and presumes the same interest rate for both loans. The calculator in the second tab allows you to set separate interest rates for each loan type and also allows you to input other estimated costs associated with homeownership including PMI, homeowners insurance, property taxes and HOA fees.

Current Redwood City mortgage rates are published under the calculator in an interactive table which allows you to quickly compare loan payments for multiple loan types using real market data.

Thinking about getting an interest-only home loan? Use this free interest-only mortgage calculator to estimate your monthly loan payments for IO and amortizing payments side-by-side.

  • Basic
  • Advanced
  • Rates
Your Interest-Only Adjustable-Rate Mortgage Payment Details


Interest Only Payment


Fully Amortized Payment


Monthly Difference

Compare Payments on Fixed vs Interest-only Mortgages

Current Mortgage Rates for a $260,000 5/1 Interest-Only ARM Home Loan

The following table highlights locally available current mortgage rates. By default they display 5-year IO ARM loans, but you can select other options using the "Products" drop down menu. Purchase rates are shown by default with refinancing offers available under the "refinance" tab.

The FRM and traditional hybrid ARM loan markets are much more liquid than interest-only loans. If no IO loans show below then consider looking at the 3/1 ARMs to see the options available across the network which have the lowest upfront monthly payments.

Re-Assessing the Interest-Only Mortgage and Its Applications

How to Calculate Monthly IO Home Loan Payments (3)

On the surface, it’s very tempting to get an interest-only mortgage. It seems cheaper than other home loans and easier to qualify for. The lower monthly payments make it a practical option for an already tight budget. But think again. Interest-only mortgages actually become pricier later down the line.

(Video) How to Calculate Interest-Only Payments (Periodic Interest) - Mortgage Math (NMLS Test Tips)

Since the 2000s, this option has fallen out of favor due to its association with the Mortgage Crisis. At the same time, there’s more to this option than meets the eye. Despite its shady reputation, these mortgages can be a viable option for some home buyers. For certain people, an interest-only mortgage may indeed be a good way to save money.

The Fundamentals of Interest-Only Mortgages

How to Calculate Monthly IO Home Loan Payments (4)

Most conventional mortgage payments consist of two parts: principal payments and interest payments. Taken together, they are known as your monthly P + I payment. Principal payments go toward paying off the amount you borrowed. Interest payments represent the fee you pay the lender for using their money. You pay these amounts through the entire amortization period of the mortgage.

In an interest-only mortgage, you only pay for the interest of your loan. This interest-only period lasts between three to ten years. It essentially defers principal payments on your mortgage. Because you only cover interest, the payments during this period are much lower. However, this period is temporary. After it lapses, you must make regular principal and interest payments.

You have the option to revert to a standard amortizing mortgage. This leads to much higher monthly payments for the remaining term. The other option is to pay off your whole balance with a lump sum. This is called a balloon payment.

How to Calculate Monthly IO Home Loan Payments (5)

Interest-only Mortgages Come in 3 Variants

  • 30-year fixed-rate mortgages have an annual percentage rate (APR) that applies to the entire amortization period. They resemble the most common type of conventional mortgage available today. The interest-period period of a fixed-rate mortgage lasts for 10 years.
  • Hybrid adjustable-rate mortgages (ARMs) have APRs that change according to an index rate. Unlike most ARMs, hybrids have fixed-rate periods that last several years before it begins to adjust. Your interest-only payments often last throughout the fixed-rate period.
  • Payment-option ARMs, as the name suggests, give you options on how you can make your payments. You can pay a standard or minimum payment, depending on how much you can afford at that time. This can go on for several years. However, be forewarned. The skipped interest payments will be added to your principal balance.

Adjustable-Rate Mortgages

On the whole, ARMs are not as popular with homebuyers as 30-year fixed-rate mortgages. Interest-only ARMs in particular are seen as especially risky. Ideally, ARMs are for people who do not plan on living in the same house for more than 30 years. These are often chosen by buyers looking for a starter home, or people who think they might need to move in a couple of years.

An ARM often comes with an introductory discounted rate. In ordinary circumstances, this can be much lower than those of fixed-rate mortgages. Once it lapses, your rate begins to adjust according to the referenced index rate. This can apply between a few months to a year in standard ARMs. Hybrid ARMs, meanwhile, have fixed-rate periods that can last for several years. Most come in denominations of three, five, seven, and ten years.

A hybrid ARM’s fixed-rate period and adjustment are expressed in fraction form. The first number represents the number of years the fixed-rate period applies. The second represents the frequency (in years) that the mortgage adjusts its APR afterward. Interest-only hybrid ARMs come in three common terms: 5/1, 7/1, and 10/1 ARMs. For example, if you take a 5/1 ARM, your rate remains fixed for the first five years of the loan. After the introductory period, the rate adjusts once a year for the rest of the term.

Note that the changing interest rate means you must be prepared for higher payments when market rates rise. For this reason, many ARM borrowers eventually refinance into a fixed-rate mortgage to avoid increasing monthly payments. But when market rates are low, ARM borrowers can take advantage of affordable monthly payments on their mortgage.

How to Calculate Monthly IO Home Loan Payments (6)

Balloon Payments

Some interest-only mortgages demand a balloon payment at the end of their term. Mortgages with balloon payments used to be common in the United States before the Great Depression. Today, however, they are rare and are heavily regulated. These are only allowed under specific circumstances outlined by Regulation Z of the Truth in Lending Act. Lenders must only grant balloon-payment mortgages according to stringent affordability guidelines.

(Video) Home Mortgage Payment Calculator Using an Excel Spreadsheet

Payment-option ARMs

A payment-option ARM lets homeowners pay what they can during their interest-only period. These mortgages have three payment options. The first is to pay the standard interest payment. The second includes the standard plus extra payment. Payments made on top of the interest goes toward lowering your mortgage principal. The third is a fixed minimum payment. This is the basic payment expected from your mortgage. You can elect to pay this minimum amount if you choose to.

If you’re running short on cash, you can choose the fixed minimum payment. This can be very convenient, especially in an emergency situation. If your house needed dire repairs, for instance, you could pay only the minimum so you can focus on construction costs. But with convenience comes risks. These missed interest payments are added to your mortgage’s principal.

Beware of Negative Amortization

How to Calculate Monthly IO Home Loan Payments (7)

Paying only the minimum puts your mortgage in a negative amortization. When this occurs, you might end up owing more money than your house is worth. This can become problematic because selling your house will be insufficient to cover the cost of your mortgage. Lenders also put an upper limit to negative amortization, which is usually 125 percent of your home’s purchase price. Once that happens, you must start making P + I payments.

Many ARMs have caps that put a limit to how high or low your APR can go. Lenders recalculate payment-option mortgages over time, usually around every five years. During this time, your new interest rate may be higher than the cap allows. This can make payment shock much more difficult to endure.


How to Calculate Monthly IO Home Loan Payments (8)

A conventional mortgage calculates your interest payments based on your remaining principal balance. At first, much of your monthly payment will go toward paying the interest you owe. The rest go toward paying your interest balance. Over time, your interest payment shrinks as you pay off more of your mortgage.

Let’s see this in action. Suppose you bought a house worth $300,000 on a 30-year fixed-rate mortgage. You pay a 20 percent down payment to avoid private mortgage insurance. This brings down your loan amount to $240,000. Your lender gives you an annual percentage rate of 2.8 percent. We’ll calculate your monthly P + I using our simple mortgage calculator.

30-Year Fixed-Rate Mortgage
Home Value: $300,000.00
Down Payment: $60,000.00

Loan Amount: $240,000.00
Rate(APR): 2.8%

In our example, your monthly P + I would be $986.15. In a conventional mortgage, your monthly payment goes toward your interest first. Your monthly interest will vary through the life of your mortgage. This is expressed in the formula below:

I = Bi

I = Your monthly interest cost
B = Your principal balance
i = Your monthly APR

The monthly APR is your current APR divided by 12. In our example, your first month’s interest payment is as follows:

I = $240,000 x (0.028 / 12)
I = $240,000 x 0.0023
I = $560.00

CategoryPayment Value
Interest Payment$560.00
Fully Amortized Payment (P + I)$986.15
Monthly Difference (Principal Payment)$426.15

If you take out an interest-only mortgage with similar terms, you only need to pay $560. On the surface, that seems like a lot of money saved. That’s nearly half of the amount your P + I would have been. The elephant in the living room, of course, is that none of those payments go toward your principal. The trouble is that you’re not building any equity past your down payment.

Your principal payment is essential for recalculating your monthly interest payment. As your principal shrinks, so does your interest. In our example, you paid $426.15 as principal on your mortgage’s first month. Your new balance will be $239,573.85.

(Video) How Principal & Interest Are Applied In Loan Payments | Principal & Interest Explained With Examples

Let’s see how this goes for the next 12 months:


Notice that your interest payments slowly go down. In a conventional fixed-rate mortgage, most of the money at first goes toward interest. Over time, more of your money goes toward principal payments. You can even speed up this process by paying extra toward your mortgage. This also helps you reduce the amount of money you pay in interest.

This isn’t the case with an interest-only mortgage. In that same ten years, your principal balance remains at $240,000 unless you decided to pay extra. In that time, you would’ve paid $67,200 in interest only. In essence, you will be paying P + I payments for a 20-year mortgage for the rest of your term. Let’s look at how much more you would have spent at that time:

Loan DetailsInterest-Only 30-Year Fixed-Rate Mortgage30-Year Fixed-Rate Mortgage
Total Interest Payments$140,912.16$115,012.80
Total Payments$380,912.16$355,012.80

All in all, you would’ve paid $25,899.36 more with an interest-only mortgage compared to a fixed-rate loan. And this is already assuming that your mortgage has a fixed APR. Avoid an interest-only loan if you want to save money on a long-term mortgage.

The Challenges of an Interest-Only Mortgage

How to Calculate Monthly IO Home Loan Payments (9)

At the end of the interest-only period, you revert to a regular mortgage with a P + I payment. This can cause what’s known as payment shock. If you weren’t ready for it, your new monthly payment can leave your finances in disarray. If your mortgage was a hybrid ARM, your payments may even skyrocket if the index rate rose. If you don’t intend to sell your house, it’s ideal to refinance into a fixed-rate mortgage if you are able.

To allay some of the shock, you could try lowering your principal balance. Paying extra toward your mortgage can keep your new P + I payments down. You may also buy yourself some time by applying for another interest-only period. However, this is an expensive proposition as you’re only delaying the time it takes to pay off your principal. You also end up paying more interest the longer you pay off your debt. This can be useful if you’re planning to sell your home. That way, you can pay off your balance with the proceeds of your home. But if you’re staying long-term in your house, it’s actually a costly arrangement.

Interest-only mortgages isn’t for everyone. Their long-term costs and consequences make them more expensive and risky in the long run. In 2020, some of the biggest lenders have restricted interest-only mortgages to jumbo loans. These large mortgages, meant for expensive properties, are much harder to apply for.

An interest-only mortgage sounds tempting if you expect to build more income in the future. They might also seem ideal if you have a lot of savings but have an irregular income stream. But unless you can afford higher payments in the future, this loan might not be right for you.

A Poster Child For Fiscal Irresponsibility

How to Calculate Monthly IO Home Loan Payments (10)

The prevalence of interest-only mortgages is among the factors behind the Subprime Mortgage Crisis of the mid-2000s. Unscrupulous lenders misled hundreds of thousands of prospective homeowners into taking these mortgages. Wooed by the prospect of low monthly payments, these buyers were taken aback by payment shock. Many of these people lost their homes to foreclosures.

A lot of people were left holding the bag when they applied for interest-only mortgages. Many of these buyers defaulted during the Subprime Mortgage Crisis of the late 2000s. Predatory lenders misled buyers into looking only at the advertised monthly payments. Because of the housing crash, these homeowners couldn’t sell their homes. Many were stuck with mortgages they couldn’t afford.

The Interest-Only Advantage

The interest-only mortgage is not meant for general purpose home buyers. People who want to settle down long-term should instead choose a conventional fully amortizing mortgage. But if you’re not building any equity with an interest-only mortgage, what is it even good for? The answer could surprise you.

Those who don’t want to stay in place can use an interest-only mortgage to their advantage. Buyers who sell their homes after a few years have no pressing need for home equity. By choosing this option, they cut down on their monthly bills. Once they sell their home, they can clear off their mortgage balance.

Among these are property investors. Many investors make money from renovating and selling fixer-upper houses. This is known as fixing and flipping. To maximize the profits they make from reselling the house, investors must buy low and sell high. Thus, a house flipper must keep all attendant costs as low as possible.

(Video) Google Sheets: Calculate monthly mortgage payments with PMT() function (2020)

The smaller monthly payments offered by interest-only mortgages are ideal for this purpose. House flippers can expect to sell their properties within at least a year or less. By paying only interest, they cut down their expenses they accrue before selling the property.

This isn’t the only time where an interest-only ARM can work for you. There are plenty of instances where you don’t need a standard fixed-rate mortgage. These often revolve around selling an older property. During a divorce, for instance, you may want to buy out your partner’s share of conjugal property and then sell it. You might want to retire elsewhere and buy a second home in anticipation. In these situations, an interest-only mortgage is a quick and inexpensive solution.

The following table summarizes the pros and cons of an interest-only mortgage:

You only need to make interest payments during the first few years of the loan (interest-only period).Deferring principal payments means you do not build home equity right away.
Your monthly mortgage payments will be cheaper.While you have time to save, you may also be tempted to spend for other costs.
The low monthly payments allow you to qualify for a larger loan amount.After the interest-only period, your monthly payments will increase significantly.
The low monthly payments may allow you to prepay your mortgage.If you make extra payments toward the principal, you might be charged prepayment penalty fees.
During the interest-only period, you can save and invest money in other worthwhile ventures.If market rates continue to increase, your payments will become unaffordable.
Monthly payments for the interest-only period qualifies as tax deductible.If you have trouble meeting expensive payments, it puts your home at risk of foreclosure.
Your total costs will be lower if you choose to sell your home at a later date.Your home sale may not be enough to cover your mortgage balance if your loan faces negative amortization.

How to Calculate Monthly IO Home Loan Payments (11)

Prepayment Penalties

Mortgages charge you for paying more than your standard payment. These prepayment penalties protect the lender. They make much of the profit from mortgages during the early years of a mortgage. Early repayment reduces the interest they earn and cuts down on their profits. By putting up these penalties, they discourage you from making larger payments early.

Another way to weather out prepayment penalties is to wait them out. Since 2014, regulations have limited prepayment penalties for the first three years after the consummation of your mortgage. However, you may plan on disposing your home long before that, especially if you plan to flip. Shop around for mortgages that don’t have penalties attached to them.

Qualifying for an Interest-Only Mortgage

It takes more than a good enough credit score to qualify for an interest-only mortgage. Since the 2000s, these mortgages were subject to new restrictions. They can no longer be used to finance entry-level home buyers.

The most important of these qualifications is proof of income. To maximize your chance of approval, you must provide ample documentation of your monthly cash flow. This assures lenders that you can afford payments once your interest-only period lapses. It also means you would not be caught in payment shock once it happens.

In addition, you must also have ample cash on hand. Proving that you have enough savings is not the only requirement. You must also make a down payment far larger than the minimum. Borrowers must also be prepared to pay 20 to 30 percent of their property’s value up front. Lenders may even demand a down payment of 50 percent for Interest-only jumbo loans.

In Summary

Assess your situation carefully before choosing this option. The biggest challenge of interest-only mortgages is dealing with the principal payments once they’re due. Will you refinance or pay the balloon payment? Will you be able to afford it? Answering these questions is key to knowing if this is the right mortgage for you.

Interest-only mortgages can be an excellent tool for some buyers. This option is ideal for homeowners who do not plan on holding onto their properties in the long term. Even if you qualify for an interest-only mortgage, it will still come with great risk. Expect some of these setbacks and prepare for them.

Paying off an interest-only mortgage to maximize your savings is a race against time. You often must sell your property before the interest-only period lapses. There is a good chance that the selling process might not go fast enough. This is especially true if the real estate markets slow down in the interim. Be prepared to pay for your mortgage far longer than you expect.

Set aside extra money for future payments well in advance. This covers your costs if it takes longer to sell off your house and will help reduce payment shock. If you plan to stay, adjust your budgets before your interest-only period lapses. This will help ease you into your new mortgage terms. Ideally, you should refinance into a fixed-rate loan for more stable payments if you plan to keep your home for the long-term.

Redwood City Borrowers: Are You Unsure Which Loans You'll Qualify For?

We have partnered with Mortgage Research Center to help Redwood City homebuyers and refinancers find out what loan programs they are qualified for and connect them with Redwood City lenders offering competitive interest rates.

(Video) Adding an "Interest Only" Period to an Amortization Schedule, 1 of 2


What is the formula for calculating monthly mortgage payments? ›

M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1].
  1. M = Total monthly payment.
  2. P = The total amount of your loan.
  3. I = Your interest rate, as a monthly percentage.
  4. N = The total amount of months in your timeline for paying off your mortgage.
10 Nov 2022

How do you calculate mortgage interest payments? ›

How Is My Interest Payment Calculated? Lenders multiply your outstanding balance by your annual interest rate, but divide by 12 because you're making monthly payments. So if you owe $300,000 on your mortgage and your rate is 4%, you'll initially owe $1,000 in interest per month ($300,000 x 0.04 ÷ 12).

How do I calculate my monthly loan payment limit? ›

Maximum monthly payment (PITI) is calculated by taking the lower of these two calculations: Monthly Income X 28% = monthly PITI. Monthly Income X 36% - Other loan payments = monthly PITI.

What is the monthly formula? ›

The monthly compound interest formula is used to find the compound interest per month. The formula of monthly compound interest is: CI = P(1 + (r/12) )12t - P where, P is the principal amount, r is the interest rate in decimal form, and t is the time.

What is the formula for monthly installment? ›

Equated Monthly Installment (EMI) Formula

The EMI flat-rate formula is calculated by adding together the principal loan amount and the interest on the principal and dividing the result by the number of periods multiplied by the number of months.

What is the formula of only interest? ›

To calculate simple interest, the formula used is (P x r x t)/100 where P, r, and t stands for principal amount, rate of interest and tenure of the deposit in years.

What is the formula to calculate loan? ›

What is Home Loan EMI?
  1. Formula for EMI Calculation is -
  2. P x R x (1+R)^N / [(1+R)^N-1] where-
  3. P = Principal loan amount.
  4. N = Loan tenure in months.
  5. R = Monthly interest rate.
  6. R = Annual Rate of interest/12/100.

What is a monthly payment on 45 000 loan? ›

Rick Bormin, Personal Loans Moderator

The monthly payment on a $45,000 loan ranges from $615 to $$4,521, depending on the APR and how long the loan lasts. For example, if you take out a $45,000 loan for one year with an APR of 36%, your monthly payment will be $$4,521.

What happens if I pay more than my monthly loan payment? ›

When you make an extra payment or a payment that's larger than the required payment, you can designate that the extra funds be applied to principal. Because interest is calculated against the principal balance, paying down the principal in less time on a fixed-rate loan reduces the interest you'll pay.

How do I calculate monthly loan payment in Excel? ›


For example, in this formula the 17% annual interest rate is divided by 12, the number of months in a year. The NPER argument of 2*12 is the total number of payment periods for the loan.

What is an interest only payment calculator? ›

Using an interest-only mortgage payment calculator shows what your monthly mortgage payment would be by factoring in your interest-only loan term, interest rate and loan amount.

What are 3 different methods of calculating interest? ›

There are three different interest calculation methods you can choose from for your loan product: Fixed Flat. Declining Balance. Declining Balance (Equal Installments)

What is the benefit of interest only? ›

What is interest only and what are the benefits? Without the need to repay capital, the monthly payments with an interest only mortgage are lower than for principal-plus-interest loans. This helps to maximise cash flow while continuing to benefit from capital growth.

How is simple interest calculated on a home loan? ›

On a simple-interest mortgage, the daily interest charge is calculated by dividing the interest rate by 365 days and then multiplying that number by the outstanding mortgage balance. If you multiply the daily interest charge by the number of days in the month, you will get the monthly interest charge.

What is the easiest way to calculate simple interest? ›

To calculate simple interest, multiply the principal amount by the interest rate and the time. The formula written out is "Simple Interest = Principal x Interest Rate x Time." This equation is the simplest way of calculating interest.

How do you manually calculate a loan payment? ›

If you have a fixed-rate loan, then calculating your monthly payment is easy: just multiply the amount borrowed by the monthly interest rate. For example, if you borrowed $3,000 at 6%, your monthly payment would be $180 ($3000 x 0.06). If you are dealing with a variable interest rate, things get tricky!

How do I calculate my loan manually? ›

EMI = [P x R x (1+R) ^N]/ [(1+R) ^N-1] P here is the principal amount, R the rate of interest charged, and N is loan tenure. Enter the values of P, R and N in the above formula to compute your monthly EMI.

How much is a $40000 loan a month? ›

The monthly payment on a $40,000 loan ranges from $547 to $4,018, depending on the APR and how long the loan lasts. For example, if you take out a $40,000 loan for one year with an APR of 36%, your monthly payment will be$4,018.

How much is a 300k loan per month? ›

On a $300,000 mortgage with a 3% APR, you'd pay $2,071.74 per month on a 15-year loan and $1,264.81 on a 30-year loan, not including escrow. Escrow costs vary depending on your home's location, insurer, and other details.

How much is a monthly payment on a 300 000 House? ›

Monthly payments on a $300,000 mortgage

At a 4% fixed interest rate, your monthly mortgage payment on a 30-year mortgage might total $1,432.25 a month, while a 15-year might cost $2,219.06 a month.

Do extra payments automatically go to principal? ›

The principal is the amount you borrowed. The interest is what you pay to borrow that money. If you make an extra payment, it may go toward any fees and interest first. The rest of your payment will then go toward your principal.

At what age should your house be paid off? ›

You should aim to have everything paid off, from student loans to credit card debt, by age 45, O'Leary says. “The reason I say 45 is the turning point, or in your 40s, is because think about a career: Most careers start in early 20s and end in the mid-60s,” O'Leary says.

What happens if I pay 2 extra mortgage payments a year? ›

Making additional principal payments will shorten the length of your mortgage term and allow you to build equity faster. Because your balance is being paid down faster, you'll have fewer total payments to make, in-turn leading to more savings.

What is the formula for mortgage payments excel? ›


The rate argument is the interest rate per period for the loan. For example, in this formula the 17% annual interest rate is divided by 12, the number of months in a year. The NPER argument of 2*12 is the total number of payment periods for the loan. The PV or present value argument is 5400.

What is the formula to calculate payment of a loan? ›

Divide the interest rate you're being charged by the number of payments you'll make each year, usually 12 months. Multiply that figure by the initial balance of your loan, which should start at the full amount you borrowed.

How do I calculate a monthly payment in Excel? ›

Salary Formula – Example #2

Here the basic salary will be calculated as follows: Basic Salary + Dearness Allowance + HRA Allowance + conveyance allowance + entertainment allowance + medical insurance.

How do you calculate payment terms? ›

Calculate the difference between the payment date for those taking the early payment discount, and the date when payment is normally due, and divide it into 360 days. For example, under 2/10 net 30 terms, you would divide 20 days into 360, to arrive at 18.


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