Your mortgage details
Change any value to see an updated illustration. LTV (loan-to-value) is the mortgage amount as a percentage of the property value. Lenders set their own LTV criteria.
Interest-only warning: your contractual monthly payment covers interest only and does not reduce the capital balance. Any overpayments you make reduce the balance and future interest.
Capital due at the end of the term:
Upfront costs
Mortgage snapshot
Ongoing payment
Full-term cost
Capital and interest over time
A labelled summary is shown when your inputs are valid.
View annual amortisation schedule
| Year | Opening balance | Payments | Interest paid | Capital repaid | Closing balance |
|---|---|---|---|---|---|
| Enter valid values to view the schedule. | |||||
Already have a mortgage? Use our UK Mortgage Overpayment Calculator to see how an extra monthly payment could reduce interest and shorten a repayment-mortgage term.
Deciding whether to buy? Compare your assumptions with our UK Rent vs Buy Calculator.
Assumptions and important information
Monthly interest is the nominal annual rate divided by 12 and the rate is assumed not to change. Overpayments may be limited by lender rules and may trigger early repayment charges—check your mortgage offer.
This illustration is not financial advice or a mortgage offer. It excludes insurance, maintenance, taxes and lender-specific charges. Last reviewed: 18 August 2026. MoneyHelper guidance and FCA mortgage guidance.
How to Calculate Your Mortgage
Enter a property price, deposit, rate, term, fees and optional overpayments to compare the monthly payment, mortgage balance and full-term cost of one fixed-rate illustration.
Enter the purchase price, deposit and product fee
Enter the property value and cash deposit. The calculator shows your deposit percentage, loan amount and LTV. Add the lender's product fee and choose whether you will pay it upfront or add it to the mortgage; a financed fee increases both the loan balance and the interest charged.
Choose the mortgage type, rate and term
Select repayment or interest-only, then use the number fields or sliders for the nominal annual rate and term. Repayment payments reduce interest and capital. Interest-only contractual payments cover interest, so any remaining capital must still be repaid at the end of the term.
Model optional overpayments
A one-off overpayment is applied before the first month's interest. A monthly overpayment is applied to capital after each month's interest has been calculated. This reduces future interest and, for repayment mortgages, may shorten the illustrated term. Check your lender's allowance and any early repayment charge before acting.
Review the payment and full-term breakdown
Use the upfront-cost, mortgage-snapshot, ongoing-payment and full-term sections together with the annual schedule. For interest-only, the highlighted capital due is the balance still to repay at term end after any overpayments. Results assume the entered rate does not change and are an illustration, not a mortgage offer.
Frequently Asked Questions
How is a mortgage monthly repayment calculated?
Monthly payments use standard amortisation. Each payment covers the interest due that month plus a slice of the capital. The formula is: <strong>P × [r(1+r)ⁿ] / [(1+r)ⁿ−1]</strong> where P = loan amount, r = monthly rate, n = number of payments.
What is a good loan-to-value (LTV) ratio?
Most lenders offer their best rates at <strong>60% LTV or below</strong>. Above 90% LTV options narrow significantly. First-time buyers can access 95% LTV mortgages through some lenders and the government mortgage guarantee scheme.
What is the difference between repayment and interest-only?
A <strong>repayment mortgage</strong> pays off both interest and capital monthly — at the end of the term you own the property outright. An <strong>interest-only mortgage</strong> contractual payment covers interest only, so the remaining capital must be repaid at the end. In this calculator, optional overpayments reduce that capital balance and future interest, but you still need a plan for the capital that remains.
Should I add the product fee to my mortgage?
Adding a product fee to the loan increases the mortgage balance, LTV and interest charged over the illustration. Paying it upfront keeps it out of the mortgage but increases your initial cash costs. Use the product-fee payment options above to compare the two scenarios.
How does the mortgage term affect total cost?
A longer term reduces your monthly payment but greatly increases the total interest paid. Compare a 25-year vs 35-year term using the selector above — the difference in total cost is often tens of thousands of pounds.
What is stamp duty, and is it included here?
Stamp Duty Land Tax (SDLT) is a separate upfront cost on property purchases, not part of your mortgage repayment. Use our <a href="/tools/uk-stamp-duty-calculator" style="color:var(--accent);font-weight:600">UK Stamp Duty Calculator</a> to calculate it alongside your mortgage costs.