Buying a home or remortgaging starts with one question: what will it actually cost me each month? A mortgage calculator UK buyers can trust gives you that answer in seconds — no spreadsheet, no guesswork, no waiting on a broker call-back.
This guide walks through exactly how our mortgage calculator works, what the numbers mean, and how to use the result to plan your next move with confidence.
What Is a Mortgage Calculator and How Does It Work?
A mortgage calculator estimates your monthly repayment based on three core inputs:
- Loan amount — the property price minus your deposit
- Interest rate — the rate on the deal you’re considering
- Mortgage term — usually 20 to 35 years in the UK
Behind the scenes, the calculator applies the standard UK amortisation formula, which works out how much of each monthly payment goes toward interest versus paying down the capital you borrowed. Early in the mortgage, more of your payment covers interest; as the balance falls, more goes toward capital.
Mortgage Payment Calculator
Estimate your monthly mortgage payment.
Illustrative estimate only. Actual payments may vary based on your mortgage, lender, fees, taxes and insurance.
Worked Example: Monthly Repayments by Loan Size
The table below shows estimated monthly repayments on a 25-year repayment mortgage at a representative 5% interest rate.
| Mortgage Amount | Monthly Repayment (25 yrs, 5%) | Total Interest Paid |
|---|---|---|
| £150,000 | £877 | £113,000 |
| £200,000 | £1,169 | £150,700 |
| £250,000 | £1,461 | £188,300 |
| £300,000 | £1,754 | £226,200 |
| £400,000 | £2,338 | £301,400 |
These figures are illustrative — your actual rate will depend on your deposit size, credit profile, and the lender you choose. Always confirm exact figures with our calculator or a mortgage adviser before making decisions.
What Affects Your Monthly Mortgage Payment?
Interest rate. The single biggest factor. As of September 2026, the Bank of England base rate sits at 3.75%, and the average lender standard variable rate (SVR) is around 6.49% — the rate you’re typically moved to once a fixed or tracker deal ends. Locking in a competitive fixed rate before your current deal expires can protect you from that jump.
Deposit size (loan-to-value). A larger deposit lowers your loan-to-value (LTV) ratio, which usually unlocks better rates. Moving from a 90% to an 80% LTV can meaningfully reduce the rate you’re offered.
Mortgage term. Stretching the term from 25 to 35 years lowers the monthly payment but increases the total interest paid over the life of the loan. Shortening the term does the opposite.
Repayment type. Repayment mortgages clear the full loan by the end of the term. Interest-only mortgages have lower monthly costs but require a separate plan (savings, investments, or sale of the property) to repay the capital — most residential lenders now require a repayment mortgage unless you meet specific criteria.
Repayment vs Interest-Only: Quick Comparison
| Repayment Mortgage | Interest-Only Mortgage | |
|---|---|---|
| Monthly cost | Higher | Lower |
| Capital owed at end of term | £0 | Full original loan |
| Who it suits | Most residential buyers | Buy-to-let, some high-net-worth cases |
| Requires a repayment plan | No | Yes |
How Much Can You Realistically Borrow?
Most UK lenders will offer 4 to 4.5 times your gross annual income, with some extending to 5–5.5 times for higher earners or certain professions. Lenders also “stress test” affordability — checking you could still cover repayments if rates rose by roughly 3 percentage points above the reversion rate — so the amount a calculator shows isn’t automatically the amount a lender will approve. For a full affordability picture, pair this calculator with an income-based borrowing check.
Frequently Asked Questions
How accurate is an online mortgage calculator?
It’s accurate for estimating the standard amortisation math — monthly interest and capital repayment — based on the figures you enter. It won’t reflect lender-specific fees, product fees added to the loan, or insurance costs, so treat the result as a strong planning estimate rather than a binding offer.
How much are repayments on a £250,000 mortgage in the UK?
At a 5% rate over 25 years, expect roughly £1,461 a month on a repayment basis. The exact figure shifts with your actual rate and term — use the calculator above with your own numbers.
Does a mortgage calculator include stamp duty?
No — stamp duty (SDLT) is a separate upfront cost based on property price and buyer status. Use our dedicated Stamp Duty guide alongside this one for the full cost picture.
What’s a good mortgage interest rate in the UK right now?
Rates move with the Bank of England base rate and lender competition, so “good” is relative to the market at the time you apply. As of late 2026, many two-year fixed deals sit in the 4–5.5% range depending on LTV, with five-year fixes priced similarly or slightly lower. Speak to an adviser for a rate matched to your circumstances.
Can I calculate my mortgage without knowing the exact interest rate yet?
Yes — use a representative rate (such as the current average for your LTV band) to get a working estimate, then refine it once you have a specific offer in hand.
Next Steps
A mortgage calculator gives you the monthly number — but the full picture includes your deposit, stamp duty, legal fees, and how much a lender will actually offer. Use our Mortgage Repayment Calculator and Loan-to-Value Calculator together to plan your budget properly, then get in touch for a free chat with one of our advisers.
This article is for general information only and does not constitute personalised financial advice. Your home may be repossessed if you do not keep up repayments on a mortgage secured against it. Figures are illustrative estimates — always confirm exact costs with a qualified mortgage adviser before making a decision.