Mortgage Repayment Calculator

How are mortgage repayments worked out?

Interest is charged each month on the balance you still owe. On a repayment mortgage, your fixed monthly payment is set so that after the last payment the balance is exactly zero: early on most of each payment is interest, and later most of it clears the loan. That is why the balance falls slowly at first, as the chart in the calculator shows. The table below uses the same formula for common loan sizes over 25 years at three illustrative rates (round numbers for comparison, not today's rates):

Why you have to enter your own interest rate

Mortgage rates move with the Bank of England base rate, swap rates and each lender's pricing, sometimes within a month. A tool that quietly assumed a typical rate would look convenient and then mislead everyone who used it after the rate went stale. So you bring a real rate: your current lender's if you are remortgaging, a quote from a broker, or one you have checked on a whole-of-market comparison site. The number you enter is only as good as how recently you checked it.

Weekly and fortnightly mortgage payments

UK lenders usually collect mortgage payments monthly, so there is no standard weekly figure. If you budget weekly, divide the year's payments by 52: the calculator shows this next to the monthly payment, which at the 5% example above is £269.81 a week. It is the same total cost spread differently, not a cheaper way to pay, unless your lender lets you make extra payments, which is a form of overpayment.

Repayment vs interest-only: the difference that matters

• • Repayment: every payment includes some of the loan, so the balance reaches zero at the end of the term. On £200,000 at 5% over 25 years that is £1,169.18 a month.
• • Interest-only: every payment covers interest alone, so the loan does not fall. The same loan costs £833.33 a month, but you still owe £200,000 at the end, in one lump sum.

How much does overpaying a mortgage save?

Overpaying reduces the balance sooner, so you pay interest on less for the rest of the term. Using £200,000 at 5% over 25 years and assuming your payment stays the same and the rate does not change:

Check your deal before you rely on this: many lenders cap how much you can overpay in a year without an early repayment charge, and the calculator does not model fees or charges.

What happens when your fixed rate ends?

Most people take a fixed deal for a few years, then move to a new deal or the lender's standard rate. Your payment is then recalculated on the balance you still owe, over the remaining term. As an illustration, £200,000 at a fixed 4% for 2 years costs £1,055.67 a month; if the rate then becomes 6%, the payment becomes £1,272.80, which is £217.13 a month more. Neither rate is a forecast. The point is to test a higher rate before you commit, which is what the fixed-deal fields and the stress-test table in the calculator are for.

Does a longer mortgage term cost more?

A longer term lowers the monthly payment but increases the total interest you pay, so a lower payment is not the same as a cheaper mortgage.

What a repayment means against real NHS take-home pay

A payment means little without the income behind it. This is something generic calculators cannot show, because they lack genuine NHS pay data. As a worked example, a full-time Band 6 at the mid-point of the 2026/27 scale takes home about £2,547.99 a month after tax, National Insurance and NHS Pension contributions, from £42,170 a year in basic pay (the same engine as the NHS Pay Calculator). Put a £180,000 repayment mortgage over 25 years against it at two illustrative rates:

The calculator above does this for your own band, point and nation. For your exact take-home, including High Cost Area Supplement or part-time hours, use the NHS Pay Calculator, and if your pay includes nights, weekends or overtime, the Rota & Take-Home Calculator.

The full NHS home-buying journey

• • How much could I borrow? The NHS Mortgage Calculator takes your band, hours, overtime and a partner's income.
• • How long will the deposit take? The Deposit & LISA Savings Calculator models a Lifetime ISA bonus.
• • What is the stamp duty? The Stamp Duty Calculator gives the band-by-band bill.
• • What will a specific loan cost? This calculator, at a rate you have checked.
• • How will a lender treat my NHS income? The role guides on the NHS Mortgages hub explain bank shifts, part-time hours and locum work.

What this calculator doesn't do

• ✕ It does not include arrangement, product or valuation fees, or early repayment charges.
• ✕ It does not know your lender's annual overpayment limit.
• ✕ It does not predict future rates: the rate after a fixed period is whatever you enter.
• ✕ It is not a lender's affordability assessment, which stress-tests higher rates and reviews your full finances.

Method and sources

Repayment mortgages use the standard amortising-loan formula; interest-only payments are the loan times the monthly rate. The schedule charges interest monthly on the opening balance, recalculates the payment over the remaining term when a fixed period ends, and applies overpayments on top of an unchanged payment, shortening the term. Take-home pay comes from our Agenda for Change data and the shared tax, National Insurance and NHS Pension engine. Everything runs in your browser. See our editorial policy and corrections policy.