PayToolkit › Mortgage Repayment Calculator

Mortgage Repayment Calculator

Your monthly payment, total interest and true total cost — for any loan size, rate and term.

Monthly repayment
Total repaid over term
Total interest
Interest-only monthly payment

Capital repayment basis with monthly compounding. Excludes product fees, insurance and rate changes after any fixed period ends.

Term length is the hidden cost lever

Stretching a £250,000 loan from 25 to 35 years cuts the monthly payment by hundreds of pounds — but can add £70,000+ of extra interest over the life of the loan. If you can afford more each month, overpaying has the same effect as shortening the term: see exactly how much interest you'd save with our Mortgage Overpayment Calculator, and check what lenders will offer you with the Mortgage Affordability Calculator.

Buying a property?

Don't forget the tax: our Stamp Duty Calculator gives your exact SDLT bill including first-time buyer relief, and if you're weighing up whether to buy at all, the Rent vs Buy Calculator finds the breakeven point.

Frequently asked questions

How is a mortgage payment calculated?

Using the standard amortisation formula: the monthly rate is the annual rate ÷ 12, and the payment is set so the loan reaches exactly zero at the end of the term — early payments are mostly interest, later ones mostly capital.

What difference does the interest rate make?

On £250,000 over 25 years, each 0.5% rate rise adds roughly £70 a month. That's why remortgaging at the end of a fixed period rather than lapsing onto the standard variable rate matters so much.

Is a longer term better?

Longer terms lower the monthly payment but cost far more in total interest. A common strategy is taking a longer term for flexibility, then overpaying — most lenders allow 10% a year penalty-free.

Does this include stamp duty and fees?

No — this models the loan itself. Product fees, valuation, legal costs and SDLT are on top; use our Stamp Duty Calculator for the tax.

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