Mortgage Repayment Calculator UK
Model: standard amortisation. The monthly payment is fixed for the whole term at the rate you enter. In real life your rate changes when a fixed deal ends, so treat the total as an illustration at one rate, not a promise. This calculator is not mortgage advice.
How the monthly payment is worked out
A repayment mortgage is worked out with the standard amortisation formula. Each month you pay interest on the balance you still owe, plus a slice of the capital. Early on, most of your payment is interest; by the end, almost all of it is capital. The formula is: monthly payment = loan × monthly rate ÷ (1 − (1 + monthly rate)−number of months). You do not need to do that by hand — the calculator does it — but knowing it explains why small changes matter so much. On a £200,000 loan over 25 years, one extra percentage point on the rate (4.5% to 5.5%) adds roughly £120 a month, and more than £35,000 of interest over the life of the loan.
An interest-only mortgage is different: you pay only the interest each month and the full loan is still owed at the end of the term. On the same £200,000 at 4.5%, interest-only costs £750 a month instead of £1,111.66 — but you would still owe £200,000 after 25 years, so you need a separate plan to repay the capital, such as savings, investments or selling the property. Most first-time buyers choose repayment, because the debt is gone at the end.
Monthly payment by loan size (example rate 4.5%, 25 years, repayment)
| Loan | Monthly payment | Total interest over 25 years |
|---|---|---|
| £150,000 | £833.75 | £100,124.62 |
| £200,000 | £1,111.66 | £133,499.49 |
| £250,000 | £1,389.58 | £166,874.37 |
| £300,000 | £1,667.50 | £200,249.24 |
| £400,000 | £2,223.33 | £266,998.99 |
These figures use the example rate of 4.5% for the whole term. Your lender’s rate will be different, and it will change over 25 years. Use the calculator above with your own rate to see your own number.
Monthly payment by term (£200,000 at example rate 4.5%)
| Term | Monthly payment | Total interest |
|---|---|---|
| 15 years | £1,529.99 | £75,397.58 |
| 20 years | £1,265.30 | £103,671.70 |
| 25 years | £1,111.66 | £133,499.49 |
| 30 years | £1,013.37 | £164,813.42 |
| 35 years | £946.51 | £197,535.66 |
A longer term cuts the monthly payment but raises the total interest a lot: stretching from 25 to 35 years saves £165.15 a month but costs an extra £64,036.17 in interest. A shorter term does the opposite. Many buyers pick the longest term they can get to keep the payment low, then overpay when they can afford it — see our Mortgage Overpayment Calculator.
Monthly payment by rate (£200,000 over 25 years, repayment)
| Example rate | Monthly payment |
|---|---|
| 3% | £948.42 |
| 4% | £1,055.67 |
| 4.5% | £1,111.66 |
| 5% | £1,169.18 |
| 6% | £1,288.60 |
| 7% | £1,413.56 |
These are example rates only, shown so you can see how sensitive the payment is. Never take a rate from a website as the rate you will be offered: your rate depends on your deposit, your credit history, the lender and the day you apply.
What else affects your monthly payment?
- Your deposit. A bigger deposit means a smaller loan and usually a lower rate, because the lender’s risk (the loan-to-value ratio) is lower. A 10% deposit on a £250,000 home means a £225,000 loan; a 20% deposit means £200,000 — about £139 less a month at the example rate.
- Fixed vs variable rate. A fixed rate locks your payment for 2, 5 or 10 years. A variable rate can rise or fall. This calculator holds one rate for the whole term, so it is most accurate for a fixed-rate period.
- Fees. Arrangement fees, valuation fees and legal fees are not in the monthly payment, but they are real costs. Some lenders let you add the arrangement fee to the loan — then you pay interest on it too.
- Overpayments. Paying even £50 extra a month cuts years off the loan. Try the overpayment calculator to see the effect.
Before you borrow, a lender runs an affordability check under the Financial Conduct Authority’s rules: they look at your income, your debts and your spending, and they stress-test whether you could still pay if rates rose. Our How Much Can I Borrow calculator shows the typical income multiple lenders use as a starting point.
Fixed rate or variable rate?
The calculator holds one rate for the whole term, but real mortgages rarely work like that. A fixed-rate deal locks your rate — and therefore your payment — for 2, 5 or sometimes 10 years. When the fixed period ends, you move onto the lender’s standard variable rate unless you switch, and the variable rate can rise or fall with the Bank of England base rate and the lender’s own decisions. A tracker mortgage follows the base rate directly, usually at a set margin above it, so your payment moves whenever the base rate moves. A discount mortgage is the lender’s standard variable rate minus a discount for a set period. Fixed rates give certainty: you know exactly what you will pay for the next two or five years, which makes budgeting easy. The price of that certainty is that you cannot benefit if rates fall, and leaving a fixed deal early usually triggers an early repayment charge. Variable and tracker deals are more flexible — you can often overpay or leave without a charge — but your payment can rise, sometimes sharply. Most first-time buyers choose a fixed rate for the certainty, and many remortgage when the fixed period ends. Whichever you choose, run the calculator at a rate one or two percentage points above the deal rate as well, so you know what the payment would look like if rates rose. If that higher payment would break your budget, the deal is too stretched.
What happens if you cannot pay?
A mortgage is secured on your home, which means the lender can repossess it if you fall seriously behind. That sounds alarming, and it is meant to be taken seriously — but repossession is a last resort, and lenders must treat borrowers in difficulty fairly under the Financial Conduct Authority’s rules. If you lose your job or your income drops, contact your lender immediately, before you miss a payment. Lenders can offer a temporary payment holiday, a switch to interest-only for a period, an extended term to lower the payment, or a reduced payment arrangement while you recover. The earlier you ask, the more options there are. Missing payments damages your credit record and makes future borrowing harder and more expensive, so even a short conversation with the lender is worth more than silence. If you are already in arrears, free debt advice is available from charities such as Citizens Advice, StepChange and National Debtline — they will help you work out a plan with the lender at no cost.
Related: How Much Can I Borrow · Mortgage Overpayment Calculator · Remortgage Calculator
Sources: Bank of England / FCA mortgage affordability rules (MCOB 11); GOV.UK “Mortgages” guidance. Rates are user-entered examples, not market rates. Checked 13 November 2026.