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Free Mortgage Overpayment Calculator

Runs entirely in your browser - no upload, no sign-up.

Live workspaceLocal processing
Mortgage scenario

Amounts have no fixed currency

Current mortgage
Overpayment plan

The one-off amount is applied after interest accrues in that payment period.

Estimated interest saved44,503.06
Time saved5 yr 11 mo
New payoff time19 yr 1 mo
Scheduled payment1,334.00per month
Interest with overpayments115,695.90
Remaining balanceOriginal Overpaying

Illustration only, not financial advice. Assumes a fixed rate, equal payment periods and unchanged scheduled payments. Fees, taxes, insurance, penalties and lender-specific daily interest are excluded.

Overpayment scheduleFirst rows from 229 payoff payments
PaymentScheduledExtraInterestPrincipalBalance
11,334.00200.00900.00634.00239,366.00
21,334.00200.00897.62636.38238,729.62
31,334.00200.00895.24638.76238,090.86
41,334.00200.00892.84641.16237,449.70
51,334.00200.00890.44643.56236,806.14
61,334.00200.00888.02645.98236,160.16
71,334.00200.00885.60648.40235,511.76
81,334.00200.00883.17650.83234,860.93
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mortgage overpayment / browser utility
01 / Overview

What does a mortgage overpayment calculator show?

A mortgage overpayment calculator estimates how extra payments change a repayment mortgage. Enter your balance, fixed annual rate and remaining term, then add recurring or one-off overpayments. It compares payoff time and interest against the original schedule, with every amount calculated privately in your browser.

02

How to use

  1. 01
    Enter the current mortgage

    Add the remaining balance, fixed annual interest rate, remaining years and contractual payment frequency.

  2. 02
    Set an overpayment plan

    Enter an extra amount for every payment, a one-off amount, or both. Choose which payment receives the one-off amount.

  3. 03
    Compare the estimates

    Review interest saved, time saved, the balance chart and the payment-by-payment schedule.

  4. 04
    Check with your lender

    Confirm any overpayment allowance, early repayment charge and how your lender applies extra payments before acting.

03

Who it's for

  • Homeowners testing whether a manageable recurring extra payment could shorten their remaining term.
  • Borrowers with a lump sum comparing a one-off principal payment with making no extra payment.
  • Budget planners seeing the separate effects of interest, scheduled principal and overpaid principal.
  • People paid weekly or fortnightly matching the model to a non-monthly repayment schedule.

This calculator uses the standard amortizing-loan formula for the scheduled payment, then models each payment period. Interest is added to the outstanding balance first; the scheduled payment and any extra principal are then deducted. Keep the same currency for every amount. No currency symbol is assumed.

These results are educational estimates, not financial advice. Your lender may calculate interest daily, recalculate payments after an overpayment, limit annual overpayments, or charge an early repayment fee. Check your mortgage terms before paying extra.

FAQ

Is my mortgage information uploaded?

No. The calculation runs locally in your browser and the values you enter are not sent to a calculation server. You can clear the form at any time. Avoid treating the estimate as a lender quote because your mortgage contract may use different timing, rounding or fee rules.

Is the mortgage overpayment calculator free?

Yes. It is free to use with no sign-up and no calculation limit. You can test recurring overpayments, a one-off payment, or both. The calculator is currency-neutral, so all amounts work as pounds, dollars, euros or another currency when you use one currency consistently.

What limits does this mortgage overpayment calculator have?

It assumes one fixed annual rate, equal payment periods and a repayment mortgage with an unchanged scheduled payment. It excludes rate changes, daily-interest timing, taxes, insurance, payment holidays, lender fees and early repayment charges. Use your lender's figures for a decision about a real mortgage.

Does overpaying reduce the mortgage term or the monthly payment?

This calculator assumes overpayments reduce principal while your scheduled payment stays the same, which shortens the term. Some lenders instead recalculate and lower the scheduled payment. Ask your lender which option applies and whether you must request a term reduction.

How is mortgage interest calculated here?

The annual rate is divided by the selected number of payment periods: 12 monthly, 26 every two weeks or 52 weekly. Each period's interest is calculated on the opening balance, then the scheduled payment and extra principal are deducted. Actual lenders may accrue interest daily.

Can a one-off payment and recurring overpayments be combined?

Yes. Enter both amounts and choose the payment number for the lump sum. The recurring amount is added at every payment until payoff. In the selected period, both extras are applied, but the final overpayment is capped so the balance cannot fall below zero.

Could my lender charge for mortgage overpayments?

Possibly. Fixed-rate and other mortgage deals may cap penalty-free overpayments or apply an early repayment charge. Rules vary by lender and contract, and this tool does not model them. Read your offer documents or contact your lender before making an extra payment.