Mortgage Calculator
Calculate your monthly mortgage payment, total interest paid, and full repayment cost for any home loan.
Most mortgage calculators show you the monthly payment and nothing else. I wanted to show the total interest paid upfront — because that number is often the most surprising part of a 30-year loan. Run your numbers and see for yourself.
Mortgage Calculator
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The mortgage calculator shows you exactly what a home loan will cost each month and in total over the full term. Enter the loan amount, annual interest rate, and repayment period to get an instant breakdown of monthly payment, total paid, and total interest charged. Most buyers focus on the monthly payment, but the total interest figure is equally important. On a £250,000 loan at 4.5% over 25 years, you pay roughly £156,000 in interest alone — more than half the original loan again. Reducing your term from 25 to 20 years on the same loan saves around £35,000 in interest at the cost of a higher monthly payment. This calculator lets you run those comparisons in seconds. Use it to size a mortgage against your income, compare fixed vs tracker rate scenarios by changing the interest rate, or evaluate whether making overpayments is worth it by testing a shorter term. Current Bank of England base rate and typical fixed-rate deals can be checked at MoneySuperMarket or Which? before entering your rate.
Working Out Your Mortgage Calculator
The Mortgage Calculator is designed to give you an accurate answer in seconds. Follow these steps:
- 1Enter your loan amount — the amount you are borrowing, not the full property price. Subtract your deposit from the purchase price to get this figure.
- 2Enter the annual interest rate. Use your mortgage offer rate or the current average for your loan type (fixed-rate or variable).
- 3Select the loan term in years. Most mortgages run 25–30 years, but a shorter term means higher monthly payments and significantly less total interest.
- 4Click Calculate. You will see your monthly payment, total amount repaid, and total interest charged. Adjust the inputs to compare different scenarios side by side.
No account or sign-up required. All calculations run locally in your browser — nothing is stored or transmitted to any server.
The Maths Behind Mortgage Calculator
Monthly Payment = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1] P = principal loan amount | r = monthly interest rate (annual rate ÷ 12 ÷ 100) | n = total number of monthly payments (years × 12)
The mortgage calculator uses the standard amortisation formula to compute equal monthly payments that fully repay both principal and interest over the loan term. The key insight behind amortisation: every monthly payment covers the interest accrued that month, with the remainder reducing the principal. Early in the loan, most of each payment is interest. As the principal falls, the interest portion shrinks and more of each payment reduces the balance. Loan term matters enormously. A 20-year mortgage on the same amount and rate has monthly payments roughly 20% higher than a 25-year mortgage, but pays significantly less total interest. The calculator makes this trade-off immediately visible. Note: this calculator assumes a fixed interest rate for the full term. Variable-rate and tracker mortgages will have different actual costs depending on how rates move. It does not include buildings insurance, life insurance, or mortgage arrangement fees, which are real additional costs in a UK loan scenario. Stamp Duty Land Tax (England/NI), Land and Buildings Transaction Tax (Scotland), or Land Transaction Tax (Wales) are also separate.
Frequently Asked Questions
How much mortgage can I afford in the UK?
UK lenders typically cap borrowing at 4–4.5× your annual income. On a £45,000 salary that is £180,000–£202,500. Couples can usually borrow 4× joint income. The monthly payment should sit comfortably below 35% of take-home pay as a rule of thumb. Use this calculator to find the loan amount that produces a payment in that range at current rates, and check your eligibility with a whole-of-market broker.
What is included in a monthly mortgage payment?
This calculator shows principal and interest only — the two core components of a repayment mortgage. In reality you will also need buildings insurance (required by most lenders) and potentially life insurance or critical illness cover. These are separate costs; add them to your monthly budget figure. Unlike the US, UK mortgages do not typically include an escrow account for insurance.
Does a shorter loan term save money?
Yes, significantly. A 20-year mortgage on the same loan amount and interest rate pays substantially less total interest than a 25-year mortgage, because the principal is repaid faster. On a £200,000 loan at 4.5%, shortening from 25 to 20 years saves approximately £20,000 in total interest. The trade-off is a higher monthly payment. Use this calculator to compare both terms.
How does a higher interest rate affect my payment?
Substantially. On a £200,000 loan over 25 years, moving from 3% to 5.5% raises the monthly payment from £948 to £1,228 — an extra £280/month and over £84,000 more in total interest. Even a half-percent rate difference adds tens of thousands to your total cost over the full term.
Is the mortgage calculator free?
Yes — free to use with no sign-up required. All calculations run in your browser and no data is stored. Run as many scenarios as you need by adjusting the loan amount, rate, and term.