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Mortgage repayment calculator

Estimate monthly payments, total interest and how the balance changes for a repayment or interest-only mortgage. You provide the interest rate; fees and future rate changes are not included.

Your figures

Repayment type

Illustrative monthly payment

£1,111.66

£200,000 over 25 years at 4.5%, repaid in equal monthly payments.

Total interest
£133,499
Total repaid
£333,499
Payments
300

Balance through the term

The balance falls as each monthly payment repays interest and principal.

Assumptions used

  • The interest rate you enter applies for the whole term.
  • Interest is charged monthly on the outstanding balance.
  • Payments are made on time, in equal monthly amounts.
  • Fees, insurance and product changes are excluded.

How the calculation works

For a repayment mortgage, the calculator uses the standard annuity formula. It turns the annual rate into a monthly rate and finds the level payment that reduces the balance to zero across the selected number of months.

monthly rate = annual rate ÷ 12

payments = term in years × 12

payment = principal × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)

At a 0% rate, the loan is divided evenly by the number of months. For interest-only, each monthly payment is the loan multiplied by the monthly rate and the principal remains outstanding at the end.

What this result does not tell you

This is an illustration, not a mortgage offer, eligibility check or recommendation. A lender may use different interest conventions and will separately assess income, spending, credit history, age, property, fees and product rules.

  • It does not model introductory periods, rate changes, fees or payment holidays.
  • It does not show whether a repayment is affordable for your household.
  • It does not compare lenders or recommend repayment versus interest-only.
  • For interest-only borrowing, you need a credible way to repay the principal.

Your home may be repossessed if you do not keep up repayments on your mortgage.

Questions people ask

Does this include mortgage fees?

No. Arrangement, valuation, broker, legal and insurance costs are excluded. If a fee is added to the mortgage, include it in the loan amount to explore the repayment effect, but remember the fee itself may have separate terms.

Why might my lender’s figure be different?

Lenders may calculate daily interest, use a different first-payment period, include fees or round at different points. Your product can also change rate during the term.

What happens if the rate is 0%?

A repayment mortgage divides the loan equally across the selected months. An interest-only illustration shows a £0 monthly interest payment while the entire principal remains outstanding.