Mortgage Payment Calculator
Enter your property price, deposit, interest rate, and term to calculate your monthly repayment on a capital repayment mortgage. Figures are illustrative — speak to a mortgage broker or lender for a personalised quote.
Calculate your mortgage repayments
All fields are required. Interest rate is the annual rate (e.g. 4.5 for 4.5%).
Related: Mortgage Overpayment · Mortgage Affordability · Stamp Duty
How the mortgage payment calculator works
A repayment mortgage is calculated using the annuity formula, which works out the fixed monthly payment needed to fully repay both the loan and all interest by the end of the term. Your payment stays the same each month, but the split between interest and principal shifts over time. In the early years, the majority of each payment is interest — because the outstanding balance is at its highest. As you pay down the principal, the interest portion shrinks and more of each payment clears actual debt.
Term length has a significant effect on both your monthly cost and the total amount you repay. A longer term reduces monthly payments but substantially increases total interest paid over the life of the mortgage. Overpaying — even by a small amount each month — reduces your balance faster and saves a disproportionate amount of interest, because every pound of principal you clear early stops accruing interest for the rest of the term. In the UK, most residential mortgages are repayment mortgages over a 25-year term, though 30 and 35-year terms are increasingly common.
Frequently asked questions
How is my monthly mortgage payment calculated?
Your monthly repayment is calculated using the annuity formula: M = P × r(1+r)^n / ((1+r)^n − 1), where P is the loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments. In plain English, the formula works out the fixed payment that will exactly pay off your loan — including all interest — by the end of the term. Early payments are heavily weighted towards interest; as the balance falls, each payment covers more principal and less interest.
What is the difference between a repayment and interest-only mortgage?
A repayment (capital and interest) mortgage means each monthly payment covers both the interest charged and a portion of the loan itself. By the end of the term, the debt is fully cleared. An interest-only mortgage means your monthly payments cover only the interest — the original loan amount remains outstanding at the end of the term and must be repaid in full. Most UK residential mortgages are repayment mortgages. Interest-only is more common on buy-to-let properties.
How much does a longer mortgage term save each month?
Extending your mortgage term reduces your monthly payment, but you pay significantly more interest overall. For example, on a £200,000 mortgage at 4.5%, a 25-year term costs around £1,111 per month with roughly £133,000 in total interest. Stretching to 35 years drops the monthly payment to around £952, but total interest rises to around £199,000 — over £66,000 more. A longer term can make a mortgage more affordable day-to-day, but the long-term cost is considerably higher.
Can I overpay my mortgage to save interest?
Yes — overpaying your mortgage reduces your outstanding balance faster, which means less interest accrues over time. Because interest is calculated on the remaining balance, even small regular overpayments can save a disproportionate amount over the full term and shorten the mortgage. Most lenders allow overpayments of up to 10% of the outstanding balance per year without an early repayment charge. Use the Mortgage Overpayment Calculator to see the exact impact of overpaying.