Loan repayment calculator

Amount, rate, term — and the true cost of the loan, not just the monthly number.

Amount £
Annual rate %
Term (years)

Monthly payment	£197.55
Total repaid	£11,852.87
Total interest	£1,852.87

Formula: payment = P × r ÷ (1 − (1+r)⁻ⁿ), r = 6.9% ÷ 12, n = 60 payments

How the formula works

Every month, interest is charged on whatever you still owe; your fixed payment covers that interest first and the remainder chips away at the balance. The amortisation formula finds the single payment that lands the balance at exactly zero on the final month:

payment = P × r ÷ (1 − (1 + r)⁻ⁿ)

where P is the amount borrowed, r the monthly rate (annual ÷ 12 ÷ 100) and n the number of monthly payments. At 0% there is no interest to spread, so the payment is simply P ÷ n — this page handles that case rather than dividing by zero.

What the monthly figure hides

Two loans with the same monthly payment can have very different true costs. Stretching £10,000 at 6.9% from 5 years to 7 drops the payment from about £198 to £150 — but lifts the total interest from about £1,850 to £2,640. The term is a price dial, not just an affordability dial. Compare offers on total repaid, and on APR rather than the headline rate, since APR must include compulsory fees.

Representative APR is not your APR. UK lenders only have to give the advertised rate to 51% of accepted applicants. The other 49% can be offered a higher rate after the credit check — re-run the numbers with the rate you are actually offered before signing.

Nothing you type is sent anywhere.

The calculator runs entirely in your browser and works offline. No cookies, no third-party scripts, no record of your finances on any server.

Common questions

Is it worth overpaying?

Usually, if there is no early-repayment charge: every pound of overpayment stops accruing interest for the rest of the term, and overpayments early in the loan save the most. Weigh it against higher-interest debt elsewhere (clear that first) and against keeping an emergency fund.

Why is my quoted payment slightly different from this?

Lenders vary in rounding, in whether interest is computed daily or monthly, and in when the first payment falls. Differences of a few pence to a couple of pounds a month are normal; a large gap usually means fees are being added to the loan.

Secured or unsecured?

The maths here is the same, but the stakes are not: a secured loan puts the asset (often your home) at risk if you default. A lower rate on a secured loan is partly you being paid for accepting that risk.

The amortisation formula is standard finance mathematics and does not go out of date. Calculations verified by automated known-answer tests (e.g. £10,000 · 6.9% · 5 years → £197.55/month). Page last reviewed: 14 August 2026. This is a calculation aid, not financial advice.

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