Mortgage repayment calculator
The monthly cost of a repayment mortgage, plus the part people forget: how much interest you pay across the whole term. Enter the loan, rate and years to see all three figures.
How the payment is built
A repayment mortgage is designed to reach zero at the end of the term. Each month the lender charges interest on whatever you still owe, and your fixed payment covers that interest plus a slice of capital. In the early years the balance is high, so most of the payment is interest and the balance falls slowly. As the balance drops the interest shrinks and more of each payment reduces the capital, which is why the loan clears faster towards the end.
Two levers move the total cost. A lower rate cuts the interest directly. A shorter term forces higher monthly payments but ends the interest sooner, often saving tens of thousands over the life of the loan.
Worked example
Borrow £220,000 at 4.50% over 25 years and the monthly payment is £1,222.83. Across the 25 years that adds up to £366,849, of which £146,849 is interest. Drop the term to 20 years and the monthly payment rises, but the total interest falls, because the debt is cleared five years sooner.
Common questions
How is the monthly payment worked out?
It uses the standard repayment formula. Each month you pay interest on the balance left, plus enough capital that the loan clears exactly at the end of the term. Early on most of the payment is interest; later most is capital. The monthly figure stays level if the rate does not change.
Why is the total interest so high?
Because interest is charged on the outstanding balance every month for the whole term. On the £220,000 example at 4.50% over 25 years you repay £146,849 in interest, on top of the amount borrowed. A shorter term or a lower rate cuts that sharply.
What is the difference between repayment and interest-only?
A repayment mortgage clears the loan by the end of the term because each payment includes capital. An interest-only mortgage pays only the interest, so the monthly cost is lower but the full balance is still owed at the end. This tool models a repayment mortgage.
Does a longer term make it cheaper?
Only month to month. Stretching the term lowers each payment but you pay interest for more years, so the total cost rises. Shortening the term does the opposite: higher monthly payments but far less interest overall.
Is the rate here fixed for the whole term?
The calculation assumes one rate for the full term, which gives a clean comparison. In practice you usually fix for two to five years and then remortgage, so the real payment changes whenever your rate does.