Finance Calc App

US Mortgage overpayment calculator

See how much interest you'd save and how many years you'd cut off your mortgage by overpaying — with a regular monthly amount, a lump sum, or both.

By Mitch Duncan Last reviewed Methodology

Mortgage details

Based on your current monthly payment of $1,461.48. Overpayments go straight to the principal. Check your lender's early-repayment limits before overpaying.

Interest saved
$44,431.86
Time saved
5y 2m
Without overpaying
Paid off in 25y 0m
Total interest $188,442.53
With overpaying
Paid off in 19y 10m
Total interest $144,010.67

Figures assume a fixed interest rate for the whole remaining term. A real mortgage rate may change at the end of a fixed period, which would alter these numbers.

Want the full picture? Should I Refinance My Mortgage? →

How mortgage overpayments save you money

A mortgage overpayment is any amount you pay above your required monthly payment. Because your scheduled payment is fixed, every extra pound or dollar goes straight to the principal — the outstanding balance. A smaller balance means less interest charged next month, and that saving compounds for the rest of the loan.

Why it works

Interest each month is charged on the remaining balance. Knock the balance down early and you remove interest from every future month at once. Overpayments are most powerful early in the term, when the balance — and therefore the interest portion of each payment — is largest.

Worked example

On a 250,000 balance at 5% with 25 years left, the required payment is about 1,460/month. Add a 200/month overpayment and you clear the loan years early and save tens of thousands in interest, because each overpayment compounds away future interest. Use the calculator to see the exact figures for your numbers.

Regular overpayments vs. a lump sum

A one-off lump sum (a bonus, inheritance, or savings) cuts the balance immediately and has the biggest single impact the earlier it lands. Regular monthly overpayments are easier to budget and steadily compress the term. Both attack the principal — the calculator lets you model either or both together.

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Frequently asked questions

How does overpaying a mortgage save money?
Your required monthly payment is fixed, so any overpayment goes straight to the principal — the balance you owe. A smaller balance means less interest is charged the following month, and that saving repeats for every remaining month. The earlier in the term you overpay, the more total interest you remove.
Is it better to overpay monthly or pay a lump sum?
Both reduce the principal. A lump sum has the biggest single impact the earlier it lands, because it removes interest from all the months that follow. Regular monthly overpayments are easier to budget and steadily shorten the term. Many people do both — a lump sum when they can, plus a fixed monthly top-up.
Should I overpay my mortgage or invest instead?
Overpaying gives a guaranteed return equal to your mortgage rate. If your rate is high, that's hard to beat risk-free. If your rate is low, investing or topping up retirement savings may earn more over time. Overpaying also wins on peace of mind and being debt-free sooner — it's partly a personal, not purely financial, choice.
Are there penalties for overpaying a mortgage?
Sometimes. Many UK fixed-rate mortgages allow penalty-free overpayments up to a limit (often 10% of the balance a year) and charge an early-repayment fee above that. US conventional mortgages usually have no prepayment penalty. Always check your mortgage terms before making large overpayments.
Does overpaying reduce my monthly payment or my term?
By default, overpaying keeps the monthly payment the same and shortens the term — you finish the mortgage earlier and pay less interest. Some lenders instead let you 'recast' the loan to lower the monthly payment over the original term. This calculator models the term-reduction approach, which saves the most interest.
When is the best time to overpay?
As early as possible. Interest is charged on the outstanding balance, which is highest at the start of the loan, so early overpayments remove the most future interest. Overpaying in the final years still helps but saves far less, because most of the interest has already been paid.

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