Mortgage Overpayment Calculator

Our Mortgage Overpayment calculator enables you to understand what amount of interest and the amount of time you can save by making a regular overpayment. When you make an overpayment after the loan has commenced, they add to your normal monthly mortgage payment. We look at the effect of making the same overpayment each month with our calculator.

We make it simple to operate. All you need to do is:

  • Put in your mortgage balance as it stands today
  • Input the mortgage interest rate that you are paying
  • Type in the remaining term of the mortgage in years
  • Put in the regular overpayment that you want to make
  • There is also the option to input a currency, but this is not compulsory

Once you have keyed these inputs, press 'Calculate' and the result will appear.

This lets you know the impact of monthly overpayments on your mortgage. It shows you how much time and money you will save. Making an overpayment will reduce the amount of interest you are charged. Our calculator is for demonstration only and should not be relied upon as an absolute figure. It uses certain assumptions and indicates the interest you will save. Some mortgages restrict the amount of cash you can overpay and have early repayment charges, so speak to your lender for details.

Some lenders take your overpayments and use them to reduce your monthly payments rather than your term, so make sure with them before you begin that the overpayments you make will have the desired effect.

Mortgage Overpayment Calculator



Details Summary
Without Overpayments With Overpayments

Mortgage Debt Over Time


The calculator assumes that the interest rate will not change for the entire mortgage term.

The calculator assumes that your monthly overpayments will be the same every month for the rest of the mortgage term.

Our mortgage overpayment calculator uses the standard formula with fixed-rate mortgage loan:

Monthly Mortgage Payment = { Rate / (1 − (1 + Rate) − N) } x Mortgage Amount


N = The Number of Monthly Payments (for a 10 year mortgage loan N = 10 x 12 = 120) ,

Rate (Monthly Interest Rate) = Decimal Rate / 12 , or Rate = (Annual Interest Rate / 100) / 12

You may also be interested in our HELOC Payment Calculator or PITI Mortgage Calculator


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