UK mortgage calculator

Use our UK mortgage calculator to estimate monthly repayments and compare how a different deposit, interest rate or term affects your budget. It models a repayment mortgage, where each payment covers interest and reduces the amount borrowed.

Your lender’s Key Facts / ESIS document (mortgage illustration) sets out the payments, costs and assumptions for a particular mortgage. This calculator helps you explore scenarios before reviewing that illustration; it cannot confirm the rate you will be offered or whether a lender will approve your application.

How to use the mortgage calculator

Adjust the four sliders:

1. Property value: the price or value of the home.
2. Deposit: the cash you will put towards the purchase. The property value minus your deposit is the loan amount.
3. Annual interest rate: the rate you want to test, expressed as a percentage. This is an assumption, not a current mortgage quote.
4. Mortgage term: the number of years over which you plan to repay the loan.

Results update automatically. You will see the monthly payment, mortgage amount, LTV, total repayments and total interest. LTV is the loan as a percentage of the property value. Total repayments means the capital and interest paid over the selected term; it excludes your deposit and other costs.

For another planning tool, see MoneyHelper’s mortgage calculators. Our calculator assumes regular capital-and-interest repayments; it does not calculate interest-only payments or an overpayment schedule.

How does the UK mortgage calculator calculate your instalment?

The calculator uses the standard amortising repayment formula, assuming the same interest rate throughout the term:

M = P * r * (1 + r)^n / ((1 + r)^n - 1)

Where:

• M is the monthly repayment.
• P is the amount borrowed: property value minus deposit.
• r is the monthly interest rate as a decimal: the annual interest rate expressed as a percentage, divided by 100, then by 12.
• n is the number of monthly payments: mortgage term in years multiplied by 12. The ^ symbol means “raised to the power of”.

For example, a £100,000 loan at an illustrative 7% over 10 years uses r = 0.07 / 12 and n = 120. This gives an estimated monthly repayment of £1,161.08. To try it above, set the property value to £125,000, the deposit to £25,000, the rate to 7% and the term to 10 years.

Total repayments are the calculated monthly payment multiplied by the number of payments. Total interest is that total minus the amount borrowed. These are illustrations using the unrounded calculation; lenders’ rounding and payment schedules can differ.

Why use a UK mortgage instalment calculator?

Use it to compare loans of £100,000, £150,000, £200,000 or £250,000, or to see what happens when you change one assumption at a time. A larger deposit reduces the amount borrowed. For the same loan and rate, a longer term usually lowers the monthly repayment but increases the total interest paid.

Compare both the monthly payment and total interest with your plans. A payment that looks manageable does not establish how much you can borrow: lenders assess income, spending, existing debts, credit history and the property before making a decision.

How does the interest rate on a mortgage affect the instalment?

For the same loan and term, a higher interest rate increases the monthly payment and total interest. Try a higher rate as well as your starting assumption to see how a change could affect your budget.

In a simplified monthly model, £100,000 at an illustrative annual rate of 6% accrues £500 of interest in the first month: £100,000 × 0.06 ÷ 12. The rest of the repayment reduces the loan balance. As the balance falls, the interest portion decreases and more of each unchanged payment goes towards capital.

That £500 is not a prediction of a lender’s first collection. The first payment can include additional interest between the release of mortgage funds and the regular payment schedule; the amount depends on the lender and completion date.

A fixed-rate deal period is different from the full mortgage term. For example, a five-year fix on a 25-year mortgage does not fix the rate for all 25 years. When the deal ends, payments may change under a new product or the lender’s variable rate. Review your options, including remortgaging, before relying on today’s payment for the whole term.

Does the mortgage calculator provide accurate values?

It provides an estimate for the loan, rate and term you select. It assumes the rate stays unchanged and payments are made as scheduled. It excludes product fees, broker fees where applicable, valuation and legal costs, insurance, overpayments and future rate changes. Budget for these separately rather than treating total repayments as the full cost of buying and owning a home.

Lenders usually require buildings insurance, while contents cover is optional. For a leasehold property, buildings cover may already be arranged by the freeholder and paid through the service charge. Check the arrangements before buying a separate home insurance policy.

Use the results as a starting point, then compare the lender’s illustration and your wider budget. Our advisers can help you review suitable mortgage options. For the wider purchase process, read buying a property in the UK step by step.