UK Mortgage Calculator — Monthly Repayments & Total Interest
Find out what a mortgage would cost each month. Enter the property price, your deposit, the interest rate and the term, and the calculator shows your monthly repayment, the total interest over the term, your loan-to-value (LTV) and a balance chart. You can switch to an interest-only mortgage to compare.
How to use the Mortgage Calculator
- Enter the property price and your deposit, either as a pound amount or a percentage.
- Enter the interest rate and the length of the mortgage in years and months.
- Choose a repayment mortgage, or interest-only to see the interest-only payment.
- Read your monthly payment, total interest and LTV, then explore the chart and repayment schedule.
How mortgage repayments are calculated
On a repayment mortgage each monthly payment covers that month’s interest plus part of the loan. Early payments are mostly interest, and the share going towards the loan grows over time. The monthly payment is calculated so that the balance reaches exactly zero at the end of the term.
A longer term lowers the monthly payment but increases the total interest, while a larger deposit lowers both. Even a small difference in rate matters: the calculator shows what your payment would be if the rate were 1% higher.
Repayment vs interest-only mortgages
With an interest-only mortgage your payments cover the interest only, so the loan balance stays the same and the full amount is due at the end of the term. Monthly payments are lower, but you need a credible plan to repay the capital, such as savings, investments or selling the property.
Loan-to-value is the loan as a percentage of the property’s value. Lenders usually offer better rates at lower LTVs, with common thresholds at 60%, 75%, 80%, 85%, 90% and 95%.
Assumptions & important information
- Interest is charged monthly at one-twelfth of the annual rate, with the same rate for the whole term.
- Real mortgages often have an initial fixed or discounted period followed by a different rate; use the Mortgage Comparison Calculator to model that.
- Fees, insurance, Stamp Duty, Land and Buildings Transaction Tax and Land Transaction Tax are not included.
- Interest rates shown in the form are examples only, not current market rates. Enter the rates from your own quote.
- This calculator gives estimates for information only. It is not financial advice and not a mortgage or loan offer. Rates, fees and lender criteria vary, so check the details with your lender or a regulated adviser. Your home may be repossessed if you do not keep up repayments on a mortgage or other debt secured on it.
Ideas & examples
- £300,000 home, £30,000 deposit: Borrowing £270,000 at 4.5% over 25 years costs £1,500.75 a month, with £180,224 interest in total. The LTV is 90%.
- What if the rate rises?: At 5.5% the same mortgage would cost £1,658.04 a month — £157.29 more. This is why many borrowers check affordability at a higher rate.
- Interest-only comparison: Interest-only at 4.5% would cost £1,012.50 a month, but you would still owe £270,000 at the end of the term.
Frequently asked questions
How much will my mortgage cost each month?
Enter the property price, deposit, rate and term and the calculator shows your monthly payment immediately. Remember to budget for other costs such as insurance, maintenance and any service charges.
What is loan-to-value (LTV)?
LTV is the amount you borrow divided by the property’s value. A £270,000 loan on a £300,000 property is 90% LTV. Lower LTVs usually unlock lower interest rates.
How is interest calculated?
The calculator charges one-twelfth of the annual rate on the outstanding balance each month. Lenders may calculate interest daily or annually, so their figures can differ slightly.
Should I choose repayment or interest-only?
Repayment mortgages clear the loan by the end of the term. Interest-only mortgages have lower payments but leave the whole loan to repay, and lenders require evidence of a repayment plan.
Does the calculator include fees and stamp duty?
No. It covers the mortgage itself. Product fees, valuation and legal costs and Stamp Duty or its equivalents are extra and depend on your circumstances.
More free tools you might need
- Mortgage Overpayment Calculator — See the interest you save and the time you cut by overpaying your mortgage.
- Mortgage Affordability Calculator — Estimate how much you could borrow and your property budget from income and outgoings.
- Mortgage Comparison Calculator — Compare two mortgage deals on rates, fees and true cost over the initial period.
- Loan Repayment Calculator — Calculate monthly repayments and total interest, and compare rates and terms.