Mortgage Repayment Calculator
Work out your monthly mortgage payment, the total you will repay and how much of that is interest over the life of the loan.
% per year
years
Monthly payment
£1,389.58
Over 300 payments
- Total repaid
- £416,874
- Total interest
- £166,874
How is a mortgage payment calculated?
A repayment (capital and interest) mortgage uses a standard annuity formula so that you pay the same amount every month. Early on, most of each payment covers interest; over time more goes towards clearing the balance.
The three things that drive your payment are the amount borrowed, the interest rate and the term (how many years you spread it over). A longer term lowers the monthly payment but increases the total interest you pay.
Why total interest matters
The monthly payment is only part of the picture. Over 25 to 30 years, interest can add up to a large share of the total repaid. Comparing the total interest across different terms and rates shows the true cost of borrowing.
Making overpayments, where your deal allows, reduces the balance faster and can save a significant amount of interest over the life of the loan.
Worked example
Borrowing £250,000 at 4.5% over 25 years works out at about £1,390 a month. Over the full term you would repay roughly £416,900 in total, of which around £166,900 is interest.
Shortening the term to 20 years raises the monthly payment to about £1,582 but cuts the total interest to around £129,600.
Please note: Results are estimates and not a mortgage offer or financial advice. Your actual payments depend on your lender, product and circumstances.
Frequently asked questions
Is this a repayment or interest-only mortgage?
It calculates a repayment (capital and interest) mortgage, where each payment reduces the balance. Interest-only mortgages work differently and are not covered here.
Does it include fees or insurance?
No. It shows the loan repayment only. Product fees, buildings insurance and any life cover are separate costs.
What interest rate should I use?
Use the rate on your current or expected deal. If you are on a fixed rate, try the rate you might revert to as well, to see how payments could change.
What happens when my fixed rate ends?
Your rate usually moves to the lender’s standard variable rate unless you remortgage. Re-running the numbers at that rate shows the potential change in payment.
Can I see a year-by-year breakdown?
Yes. The results include an optional amortisation summary showing how your balance falls each year.
Figures last reviewed on 13 August 2025.
Related calculators
Mortgage Affordability
Get a rough idea of how much you might be able to borrow, your likely property budget and an estimated monthly payment.
Open calculatorStamp Duty
Estimate the property purchase tax you will pay in England, Scotland or Wales, including first-time buyer relief and the second-home surcharge.
Open calculatorCompound Interest
Calculate how an initial amount plus regular contributions grows with compound interest, and see a simple visual of that growth.
Open calculatorSavings
See how much your savings could grow with regular monthly contributions and compound interest over time.
Open calculator