Loan Repayment Calculator

Enter the amount, the rate and the term. Drag the sliders to see how each one moves the payment.

What the numbers mean

The monthly payment is calculated with the standard amortisation formula, the same one banks use. Every payment is part interest and part principal, and the split shifts over time: early payments are mostly interest, later ones mostly principal.

That is why the year-by-year breakdown is worth opening. On a 25-year mortgage, the balance after five years is usually far higher than people expect, and seeing it is more useful than the headline figure.

Total interest is the number to watch

Stretching a loan over a longer term lowers the monthly payment and raises the total interest, often dramatically. Try the same amount over five years and over ten — the monthly figure looks kinder and the total cost does not.

This calculator assumes a fixed rate and equal payments. Variable-rate loans, offset accounts and early repayment charges will all change the real figure, so treat this as a planning tool rather than a quote.

How this is worked out

The monthly payment uses the standard amortisation formula M = P·r(1+r)^n / ((1+r)^n − 1), where P is the principal, r the monthly rate and n the number of payments. A 0% rate falls back to simple division, since the formula divides by zero there.

Common questions

Does this include fees or insurance?

No. It calculates principal and interest only. Arrangement fees, insurance and taxes sit on top and vary by lender.

Why is so much of my early payment interest?

Interest is charged on the balance outstanding, which is highest at the start. The split shifts towards principal every month — open the year-by-year breakdown to see it.

Is this accurate for a mortgage?

For a fixed-rate repayment mortgage, yes. Variable rates, offset accounts and overpayments all change the real figure.