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Buying Budget

Mortgage Repayment Calculator

Estimate only

Enter a mortgage amount, an interest rate assumption and a term to see an illustrative monthly payment, the total you would repay and how much of that is interest. The rate you enter is an assumption — real payments depend on the product you are accepted for.

Repayment type

Estimated monthly payment

£1,169.18

Over 25 years at 5%, capital and interest.

Total repaid

£350,754

Total interest

£150,754

Capital repaid by end of term

£200,000

Estimate only

This illustration assumes the same interest rate for the whole term. In practice most UK mortgages have a fixed or discounted period and then move to the lender's variable rate, so your payment is likely to change.
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How this calculation works

Repayment mortgages use the standard annuity formula, applied monthly. Interest-only payments are simply the monthly interest on the balance, with the capital outstanding throughout. The amortisation table applies the payment month by month and groups the result into years.

M = P · r ÷ (1 − (1 + r)^−n)
P = mortgage amount, r = annual rate ÷ 12, n = term in months
Interest-only: M = P · annual rate ÷ 12

Assumptions

  • One constant interest rate for the whole term.
  • Interest is calculated monthly on the outstanding balance.
  • No product fees, insurance or overpayments are included.

Limitations

  • Lenders calculate interest daily, monthly or annually; small differences in the monthly figure are normal.
  • Fixed-rate periods, rate changes and payment holidays are not modelled.
  • This is an illustration, not a quotation or an offer.

Last reviewed: 1 September 2026 · Calculation version 1.0.0

Reading a repayment beyond the monthly headline

Term and interest move in different directions

A repayment mortgage pays both interest and capital. Extending the term spreads the capital over more payments, usually reducing the monthly cost while increasing total interest at the same rate. Compare the same loan at 25 and 30 years and read both outputs. A smaller payment alone does not make the longer option cheaper, and the model assumes the entered rate lasts for the whole term.

Interest-only is not a lower-cost repayment plan

A £200,000 interest-only loan at 6% costs £1,000 a month in interest, but the £200,000 capital still remains at the end unless you repay it separately. The lower payment cannot be compared with a repayment mortgage without considering that final debt and a credible repayment strategy. Interest-only eligibility depends on the lender; this calculator does not assess whether you qualify.

Rate changes and product fees

A fixed deal may last only part of the mortgage term. The lifetime total is therefore a constant-rate illustration, not a prediction. Run the remaining balance through the calculator at a higher rate to examine a future reset. Product fees, insurance and early repayment charges are not automatically included in the monthly mortgage figure. If a fee is added to the loan, interest may be charged on it too.

Further reading: MoneyHelper — repayment and interest-only mortgages. Examples are illustrations using stated inputs, not quotes or personal recommendations.

See our method and limitations or report a correction.

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