How is the calculation done?

We compute the standard amortization schedule, then simulate month-by-month with the overpayment added, counting months until the balance reaches zero.

Does this assume I start overpaying from day one?

Yes, the calculator assumes the overpayment is made from the first month. Starting overpayments later will reduce (but not eliminate) the savings.

What if my lender charges early-repayment fees?

This tool doesn't model early-repayment fees. Check your mortgage terms — some lenders cap annual overpayments at 10% of the balance.

Is my data stored anywhere?

No. All calculations happen in your browser. No data is transmitted or saved.

MORTGAGE OVERPAYMENT CALCULATOR

Enter your mortgage details and a monthly overpayment amount to see how many months you save and how much less interest you pay. Everything runs in your browser.

Loan Amount ($)

Annual Interest Rate (%)

Loan Term (years)

Monthly Overpayment ($)

Monthly Payment$1,111.66without overpayment

Months Saved73months

Interest Saved$36,280.39

New Payoff

25 yrs18 yrs 11 mo

Comparison

Original

25 yrs · $133,499.49 total interest

With Overpayment

18 yrs 11 mo · $97,219.09 total interest

How to use the mortgage overpayment calculator

1
Enter your loan amount, annual interest rate, and original loan term in years.
2
Enter the extra amount you plan to pay each month on top of your regular payment.
3
See instantly how many months you save and how much less interest you'll pay.

Questions

How is the calculation done?: We compute the standard amortization schedule, then simulate month-by-month with the overpayment added, counting months until the balance reaches zero.
Does this assume I start overpaying from day one?: Yes, the calculator assumes the overpayment is made from the first month. Starting overpayments later will reduce (but not eliminate) the savings.
What if my lender charges early-repayment fees?: This tool doesn't model early-repayment fees. Check your mortgage terms — some lenders cap annual overpayments at 10% of the balance.
Is my data stored anywhere?: No. All calculations happen in your browser. No data is transmitted or saved.