Mortgage Repayment Calculator
Enter how much you are borrowing, the interest rate and the term to see your monthly repayment, the total you will pay and the interest cost — with an interest-only comparison. Adjusting the rate or term and recalculating is the quickest way to see what a remortgage or a shorter term would really change.
How it works
Repayment mortgages use the amortising formula: each payment covers that month's interest plus some capital, so the balance falls and the interest share shrinks over time. £200,000 at 4.5% over 25 years costs about £1,112 a month.
Look inside that first payment: month one's interest is £200,000 × 4.5% ÷ 12 = £750, so of the £1,112 only about £362 actually reduces the loan. This is why the balance seems to barely move in the early years — and why the same payment clears capital far faster near the end, when the interest share has shrunk.
Interest-only: monthly cost = loan × rate ÷ 12 (£750 on the same example) but the full £200,000 remains due at the end — lenders require a credible repayment plan. The gap between the two figures — £1,112 versus £750 here — is exactly the capital you are repaying each month on the repayment basis.
Term choice moves both numbers in opposite directions: the same £200,000 at 4.5% costs about £1,112 a month over 25 years (£133,000 total interest) but about £1,013 over 30 years — a saving of only £99 a month in exchange for roughly £165,000 of total interest, £32,000 more over the life of the loan.
Rates are fixed only for the deal period (2, 5, 10 years); after that you move to the lender's standard variable rate unless you remortgage. Overpaying (typically up to 10% a year penalty-free) shortens the term dramatically.
What the result includes and leaves out: it covers the loan itself — monthly payment, total repaid and total interest at a single unchanging rate. It does not include arrangement or valuation fees, insurance, or the rate changes that follow the end of a fixed deal. A common mistake is entering the 2- or 5-year deal length as the term: the term is the full payoff period (say 25 years), while the deal length only fixes the rate for part of it.
FAQ
How much are repayments on a £200,000 mortgage?
At 4.5% over 25 years, about £1,112 a month on repayment — £333,000 in total, of which £133,000 is interest. Over 30 years the monthly drops to about £1,013 but total interest rises to £165,000. Enter your own figures above for exact numbers.
Should I pick a shorter or longer mortgage term?
Shorter terms cost more monthly but save enormous interest: £200,000 at 4.5% costs about £133,000 interest over 25 years versus about £75,000 over 15. Longer terms buy monthly headroom at a steep lifetime price. Many lenders let you overpay ~10% a year, letting you shorten the term flexibly without committing.
What happens when my fixed rate ends?
You roll onto the lender's standard variable rate — usually far higher. Remortgaging to a new deal 3-6 months before the fix ends is standard practice; rate changes of even 1% move the payment on a £200,000 loan by roughly £110 a month. Recalculate here with candidate rates before choosing.
Why does my mortgage balance fall so slowly in the early years?
Because interest is charged on the outstanding balance, and the balance is at its peak at the start. On £200,000 at 4.5%, the first month's interest is £750 — meaning only about £362 of a £1,112 payment clears capital. Each month the interest share shrinks slightly and the capital share grows, so repayment accelerates naturally towards the end of the term without the payment ever changing.
What is the difference between repayment and interest-only?
On repayment, each payment includes capital, so the loan is guaranteed to reach zero at the end of the term — £1,112 a month on £200,000 at 4.5% over 25 years. On interest-only you pay just £750 a month on the same figures, but you still owe the full £200,000 at the end and must have a credible plan to repay it. The calculator shows both figures so you can see the £362 of capital hiding in the repayment number.
What costs does this calculator not include?
It models the loan alone at one constant rate. Arrangement fees, valuation and legal costs, insurance, and any rate change after your fixed deal ends are all outside the calculation. In practice a mortgage held for 25 years will pass through several deals at different rates, so treat the total-interest figure as a like-for-like comparison tool between scenarios rather than a prediction of your lifetime cost.
How much difference does overpaying make?
Overpayments go straight at the capital, and every pound of capital removed stops generating interest for the rest of the term — which is why lenders cap penalty-free overpayments, typically at 10% of the balance a year. Because early payments are mostly interest, overpayments made early in the term do the most work. Model it here by shortening the term until the monthly payment matches what you could genuinely afford.