Interest-Only Mortgage Calculator

Created by Mateusz Tkaczyk
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Dec 02, 2020

This interest-only mortgage calculator is a tool that will help you find the monthly payment if you were to take out this specific type of mortgage loan. The result shows you the amount of interest you have to pay.

The interest-only mortgage payment calculator can be used on different types of interest-only loans or to calculate your interest value on other loans or mortgages. If you are interested in the topic, go to the next section to find out more about what the interest-only mortgage is.

What is an interest-only mortgage?

An interest-only loan or mortgage is a type of loan which makes the borrower pay only interest for the provided period. In other words, you are not paying off your debt (principal value), just the interest.

As only interest is paid each month, your debt remains the same. After the specific period is over, you will have to pay back your debt either as a lump-sum or monthly with different terms.

In this interest-only mortgage calculator, you may find additional values in the advanced mode. Provide the length of the interest-only loan period and you will discover how much you will have to pay for the entire time with the provided conditions.

Pros and cons of interest-only loans?

Here are the Advantages of an interest-only mortgage loan:

  1. The monthly payments are smaller than a typical mortgage over the period without the principal.
  2. The mortgage interest rates are often small. You can invest the money you saved from not paying the principal value.
  3. Managing your household's budget is easier due to small and stable interest-only mortgage payment.
  4. If you expect that your salary will increase with time, it will be easier for you to payoff the debt in the future.

There are, however some disadvantages to an interest-only mortgage loan:

  1. As the principal value is not paid, your mortgage remains the same - your debt does not decrease. Interest-only loans do not amortize during the interest-only period.
  2. You will still have to repay the principal value of your mortgage. It means that you will need to pay a higher amount each month after the interest-only period (where you pay back the interests and principal together) or pay off the principle as a lump-sum.
  3. Having a high amount to pay in the future may be risky as you cannot be sure about your future situation. For example, becoming unemployed or being faced with unexpected additional costs may lead to financial troubles.

Interest-only mortgage payment example

Imagine you are planning on buying a new house, and, for that reason, you need to borrow $350,000. According to the terms of your mortgage, it will be an interest-only loan during the first ten years, with an annual interest rate of 4%.

The next step is to calculate your payment for this period using the interest-only mortgage calculator. If you want to calculate the monthly payment, choose this option in the payment frequency field.

In this example, we are calculating monthly payments based on the yearly interest rate. It means that we have to divide 4% by 12 months.

Yearly payment = Loan amount * Annual Interest rate

Yearly payment = $350,000 * 0.04 = $14,000

Monthly payment = $350,000 * 0.04 / 12 = $14,000 / 12 = $1,166.67

Based on the example terms, you will have to pay $1,166.67 each month for the next ten years. After this period, you will still have $350,000 debt that has to be paid off in a lump-sum or with higher monthly payments.

Mateusz Tkaczyk
Loan amount
Annual interest rate
Payment frequency
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