How to use the UK mortgage calculator
- Enter the Property price and your Deposit, either as a percentage or in pounds. The calculator shows the loan amount and the loan to value (LTV).
- Add the Interest rate and the Term in years and months, then choose Repayment, Interest-only or Part and part.
- If your deal rate only lasts a few years, open Introductory deal, then a follow-on rate, tick the box and enter the deal length and the rate you expect afterwards.
- To see what overpaying does, open Overpayments and add an extra amount each month, each year, or one-off lump sums.
- Read the monthly payment, total interest, total repaid and the date you would be mortgage-free, then check the balance chart and the yearly amortisation schedule. Copy results puts a summary on your clipboard.
- Switch to How much can I borrow? for a quick estimate based on income and on the monthly payment you can afford.
How the mortgage payment is worked out
A repayment mortgage is an amortising loan. Interest is charged each month on the balance you still owe (the yearly rate divided by 12), and the fixed monthly payment is set so that the last payment clears the loan exactly at the end of the term. Early on, most of each payment is interest; towards the end, most of it repays capital. The schedule on this page shows that shift year by year.
With an interest-only mortgage the monthly payment covers just the interest, so the balance does not go down. The whole loan is still owed at the end of the term and has to be repaid from savings, investments, the sale of the property or another plan your lender accepts. Part and part splits the loan: one part is interest-only and the rest is a repayment mortgage.
Most UK mortgages start on a fixed or tracker deal for two to five years. When the deal ends you move to the lender's follow-on rate unless you remortgage or switch product. The calculator handles this in two stages: it runs the deal rate until the deal ends, then recalculates the payment on the balance left over the remaining term at the follow-on rate. Use the follow-on rate box to test the rate you might move on to.
Worked example
A £300,000 home with a 10% deposit needs a £270,000 loan, an LTV of 90%. At 4.5% over 25 years on a repayment basis the monthly payment is about £1,500.75. Over the full term you would pay about £180,224 in interest and £450,224 in total. The same loan on an interest-only basis costs £1,012.50 a month, but the £270,000 is still owed at the end.
Overpaying £200 a month on the repayment mortgage clears it in about 20 years and 2 months instead of 25 years and cuts the interest to about £141,069, a saving of roughly £39,155. That is the effect of every extra pound reducing the balance that interest is charged on.
How much can I borrow?
Lenders usually start with an income multiple. Many cap lending at around 4 to 4.5 times your yearly income (combined, for a joint mortgage), and some go higher for certain professions or larger incomes. Treat that as a typical range, not a promise. Lenders then run an affordability check: your income, regular spending, credit commitments and whether you could still pay if rates rose. This page mimics that last part with a stress-test rate: it shows the loan your chosen monthly payment supports at your rate and at the higher stress rate, and takes the lower of the stress-tested figure and the top income multiple as a cautious estimate. Add your deposit to get a property budget, then check the stamp duty on that price.
Why your lender's figures may differ
- Fees. Arrangement or product fees added to the loan increase the balance and the payment.
- Interest calculation. Some lenders charge interest daily, so payments can differ by a few pounds a month from a monthly calculation.
- Overpayment rules. Many fixed-rate deals allow overpayments of up to about 10% of the balance each year without an early repayment charge. Some lenders use overpayments to lower your monthly payment instead of shortening the term.
- Rate changes. Tracker and variable rates move, so payments after a fixed period are an estimate.
To see what you actually take home each month before budgeting for a mortgage, use the UK salary calculator. For other borrowing, try the UK loan calculator or the UK debt calculator, and browse all salary and money calculators.
Frequently asked questions
How is a monthly mortgage payment calculated?
For a repayment mortgage the payment is P × r ÷ (1 − (1 + r)−n), where P is the loan, r is the yearly interest rate divided by 12 and n is the number of monthly payments. For an interest-only mortgage it is simply the loan × the yearly rate ÷ 12.
How much does overpaying my mortgage save?
It depends on the rate, the balance and how early you overpay. Each overpayment cuts the balance that future interest is charged on, so early overpayments save the most. Add your overpayments above to see the interest and time saved.
What is loan to value (LTV)?
LTV is the loan as a percentage of the property's value. A £270,000 loan on a £300,000 home is 90% LTV. Lower LTV bands usually come with lower interest rates.
How much can I borrow for a mortgage in the UK?
Many lenders lend around 4 to 4.5 times your yearly income, subject to an affordability check of your spending, debts and ability to cope with higher rates. The How much can I borrow? tab gives a cautious estimate, not an offer.
What happens when my fixed-rate deal ends?
You usually move to the lender's follow-on rate, often a standard variable rate, unless you switch to a new deal or remortgage. Turn on the follow-on rate option to see how your payment could change.
Does this include stamp duty or fees?
No. It covers the loan only. Work out stamp duty with the stamp duty calculator and add any lender, survey and legal fees to your budget.
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