Calculate monthly mortgage payments, total interest and view an amortization schedule. Free online mortgage calculator with extra payment support.
What Is Mortgage Calculator?
A mortgage calculator estimates your monthly repayments based on the loan amount, interest rate and term. It uses the standard amortisation formula to show exactly how much you will pay each month and how much of that goes to interest versus principal over the life of the loan.
Understanding your mortgage numbers before approaching a lender is crucial. Even small differences in interest rate — 4% versus 4.5% — can mean tens of thousands of pounds over a 25-year term. This calculator lets you compare scenarios side by side so you can make informed decisions about deposit size, loan term and acceptable interest rates.
How to Use This Tool
Enter the property price and your deposit amount.
Set the annual interest rate offered by your lender.
Choose the loan term in years (typically 25 or 30).
View your estimated monthly repayment, total repaid and total interest.
Adjust the values to compare different scenarios and see how changes affect the cost.
Tips & Best Practices
A larger deposit reduces your loan-to-value ratio and typically qualifies you for better interest rates.
Compare total cost over the full term, not just monthly payments — a longer term has lower monthly costs but much higher total interest.
Consider overpayment allowances — most UK mortgages allow up to 10% annual overpayment, which significantly reduces total interest.
Factor in additional costs like stamp duty, solicitor fees and survey costs when budgeting.
Common Use Cases
Estimating monthly repayments before starting your property search.
Comparing fixed-rate offers from different lenders.
Calculating how much deposit is needed to reach a target monthly payment.
Understanding the total cost difference between a 25-year and 30-year mortgage term.
Frequently Asked Questions
How is my monthly mortgage payment calculated?
The calculator uses the standard amortization formula: M = P[r(1+r)^n]/[(1+r)^n-1], where P is the loan amount, r is the monthly interest rate, and n is the total number of payments.
Can I see how extra payments reduce my mortgage?
Yes. Premium users can add monthly extra payments and see how much interest they save and how many years they shave off the loan term.