Mortgage Affordability Calculator
Estimate how much you may be able to borrow based on income, deposit and commitments.
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UK Mortgage Repayment Calculator
Estimate your monthly mortgage payment, total interest and total repayment cost using a repayment or interest-only mortgage calculation.
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- ✓Repayment and interest-only estimates
- ✓Monthly payment, total interest and full cost
- ✓Updates instantly as you type
Calculate your mortgage repayments
Enter your mortgage amount, interest rate and term. The results update automatically, so you can test different rates and terms quickly.
How to use this calculator
- Enter the mortgage amount you expect to borrow.
- Add the annual interest rate you want to test.
- Choose the mortgage term in years.
- Select repayment or interest-only to compare the monthly cost.
Mortgage repayment formula
monthly_rate = annual_rate / 100 / 12
total_months = mortgage_term_years × 12
monthly_payment =
mortgage_amount ×
(monthly_rate × (1 + monthly_rate)^total_months) /
((1 + monthly_rate)^total_months - 1)
For a repayment mortgage, the formula spreads the capital and interest across the full term. For interest-only, the monthly payment is simply the loan balance multiplied by the monthly interest rate.
Estimated monthly payment
£1,461.48
Estimated monthly repayment based on your mortgage amount, rate and term.
Total interest over term
£188,442.53
This is the estimated interest paid if the rate stayed the same for the full term.
Total paid over term
£438,442.53
This includes the original mortgage balance plus estimated interest.
Balance remaining at end
£0.00
A repayment mortgage is designed to reduce the balance to zero by the end of the term.
Repayment estimate
25-year term
This is an estimate only. It does not include arrangement fees, valuation fees, insurance, early repayment charges or lender affordability checks.
Ready to act on your result?
Once you know the monthly payment you are comfortable with, compare mortgage deals or speak to a broker before choosing a product.
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What your mortgage result means
The monthly payment is the estimated amount you would pay each month if the mortgage rate, balance and term stayed as entered. For a repayment mortgage, each payment includes both interest and part of the original loan.
The total interest figure shows how much borrowing could cost over the full mortgage term. This is why a lower monthly payment is not always cheaper overall: stretching the same mortgage over more years often increases the total interest paid.
For interest-only mortgages, the monthly payment is lower because it does not repay the original balance. The calculator shows the balance remaining so you can see the amount that still needs to be repaid later.
How mortgage repayments work
A repayment mortgage is designed so the balance gradually falls to zero by the end of the term. In the early years, a larger share of each payment usually goes towards interest because the outstanding balance is still high.
As the balance reduces, more of each monthly payment goes towards repaying the capital. That shift is called amortisation. It is the reason your monthly payment can stay broadly level while the split between interest and capital changes over time.
The interest rate has a major effect on the result. A small change in rate can make a noticeable difference to monthly payments, especially on larger mortgages. That is why many borrowers compare fixed-rate, tracker and standard variable rate options before choosing a deal.
The mortgage term also matters. A longer term can make the monthly payment feel more affordable, but the debt runs for longer and interest has more time to build up. A shorter term usually costs more each month but can reduce the total amount paid overall.
An interest-only mortgage works differently. You pay the interest each month, but the original balance does not reduce. That means you need a separate repayment plan, such as savings, investments or a future property sale, depending on what the lender accepts.
What affects your mortgage repayment
- Mortgage amount: The more you borrow, the higher your monthly payment and total interest are likely to be.
- Interest rate: A higher rate increases the monthly payment and the long-term cost of borrowing.
- Mortgage term: A longer term normally reduces the monthly payment but can increase the total interest paid.
- Mortgage type: Repayment mortgages reduce the balance, while interest-only mortgages leave the original loan outstanding.
- Fees and product costs: Arrangement fees and other charges can make a lower-rate deal less attractive than it first appears.
- Future rate changes: Your payment can change when a fixed deal ends or if you are on a variable or tracker rate.
Mortgage repayment calculator FAQs
How do I calculate my monthly mortgage payment?
A repayment mortgage payment is calculated using the mortgage amount, monthly interest rate and the number of monthly payments. This calculator uses the standard repayment mortgage formula to estimate the payment needed to clear the balance by the end of the term.
How much would a £250,000 mortgage cost per month?
A £250,000 repayment mortgage over 25 years at 5% is estimated at about £1,461.48 per month. The exact figure changes if the rate, term, fees or mortgage type are different.
What happens if mortgage rates go up?
If your mortgage rate rises, the monthly payment usually rises too unless you are protected by a fixed-rate deal. The impact is bigger when the outstanding balance is high or the remaining term is long.
Is repayment or interest-only cheaper monthly?
Interest-only is usually cheaper each month because you are only paying the interest. The trade-off is that the original mortgage balance remains unpaid, so you need a credible way to repay it later.
How much interest will I pay over the life of my mortgage?
Total interest depends on the amount borrowed, the rate and the term. A longer mortgage term can reduce your monthly payment, but it often increases the total interest because you are borrowing for more years.
Does this calculator include mortgage fees?
No. This calculator estimates the mortgage payment using the loan amount, interest rate and term only. Arrangement fees, valuation fees, legal costs and insurance are not included.
Key terms used in this calculator
These mortgage terms explain the main concepts behind the calculation.