Mortgage Repayment Calculator UK — Monthly Payments & Interest
Use our free UK mortgage repayment calculator to work out your monthly payments, total interest and total amount repaid on a repayment or interest-only mortgage. Enter the property price, deposit, mortgage term and interest rate to see an instant breakdown. The calculator uses the standard annuity formula that most UK lenders apply.
Whether you are a first-time buyer working out what you can afford, a homeowner considering remortgaging, or simply exploring different term lengths and rates, this tool gives you the numbers you need to make an informed decision. Even small changes in interest rate or term length can have a dramatic impact on your total costs. A one percentage point increase on a £250,000 mortgage over 25 years adds over £43,000 in total interest, so it pays to understand the figures before committing.
How Mortgage Repayments Are Calculated
UK repayment mortgages use a standard annuity formula. Each monthly payment covers a portion of the interest and a portion of the capital. In the early years, most of your payment goes towards interest, but as the outstanding balance shrinks, more of each payment reduces the capital. By the end of the term, the loan is fully repaid. Interest-only mortgages work differently: you only pay the interest each month, so the capital balance remains unchanged and must be repaid in full at the end of the term through a separate repayment vehicle such as savings or investments.
The Bank of England base rate influences mortgage rates across the market. Tracker mortgages move directly with the base rate, while fixed-rate deals lock in a set rate for a period (typically 2 or 5 years). For the latest guidance on mortgage regulation and your rights as a borrower, visit the FCA section on GOV.UK.
Choosing the Right Mortgage Term
The most common UK mortgage term is 25 years, but terms of 30, 35 and even 40 years are increasingly popular, especially among first-time buyers. A longer term reduces your monthly payment but increases the total interest you pay. For example, a £200,000 mortgage at 5% costs £1,169 per month over 25 years (total interest: £150,754) but just £1,043 per month over 35 years (total interest: £238,087). That is an extra £87,000 in interest for the privilege of lower monthly payments.
Overpaying your mortgage, where allowed, is one of the most effective ways to reduce total interest and shorten your term. Most lenders permit overpayments of up to 10% of the outstanding balance per year without penalty. For related calculations, try our stamp duty calculator to see the upfront costs of buying, or use the rent vs buy calculator to compare the long-term cost of renting against purchasing.
First-Time Buyer Mortgage Tips
First-time buyers benefit from stamp duty relief on properties up to £425,000 and can access government schemes such as the Lifetime ISA (which provides a 25% bonus on savings up to £4,000 per year towards a deposit). A larger deposit not only reduces the amount you need to borrow but also unlocks lower interest rates, as lenders offer their best deals at lower loan-to-value ratios. Even increasing your deposit from 5% to 10% can reduce your interest rate by 0.3 to 0.5 percentage points.