How mortgage overpayments work
The calculator keeps your normal monthly payment the same and adds your overpayments, so the mortgage is cleared early and less interest builds up.
Some lenders lower your monthly payment after an overpayment instead of shortening the term. Ask yours which it does; this calculator shows the term getting shorter.
Worked example
On a £200,000 mortgage at 4.5% with 25 years left, the normal payment is £1,111.66. Overpaying £200 a month saves £36,280.39 in interest and clears the mortgage 6 years 1 month early. Overpaying £500 a month saves £63,886.72 and 11 years.
Overpayment limits and charges
Many fixed and discounted deals let you overpay up to 10% of the balance each year without an early repayment charge; above that, a charge can apply. Variable-rate mortgages often allow unlimited overpayments.
Overpaying usually makes sense when your mortgage rate is higher than what your savings earn after tax, and once you have an emergency fund.
What this calculator assumes
The calculator takes your mortgage balance and rate, works out the normal monthly payment over the time left, then replays the loan month by month with your overpayments added. It assumes your lender keeps the payment the same and shortens the term.
It leaves out early repayment charges, annual overpayment limits and any change of rate, so check your own terms before relying on the saving.
Inputs for the mortgage overpayment calculator
Amount you owe
Your current mortgage balance.
Interest rate (per year)
Your current interest rate.
Time left to repay
How many years are left on the loan.
Extra each month
The amount you'll pay on top of your normal payment each month. Enter 0 for none.
One-off lump sum now
A single overpayment made now. Enter 0 for none.
CALCULATOR QUESTIONS
Mortgage overpayment calculator questions
How much can I overpay my mortgage?
Many deals allow up to 10% of the balance each year without an early repayment charge. Check your terms.
Is it better to overpay or save?
Overpaying usually wins if your mortgage rate is higher than your after-tax savings rate, once you have an emergency fund.
Will overpaying reduce my monthly payment?
It depends on the lender. Some shorten the term, others lower the payment.
How much would £200 a month save?
On £200,000 at 4.5% with 25 years left, £36,280.39 and 6 years 1 month.