Mortgage Calculator UK

A mortgage calculator turns a property price, a deposit, a term and an interest rate into the numbers that matter: what you would pay each month, how much interest you would pay in total and how long it would take to clear the loan. Our free UK mortgage calculator works out repayment and interest-only mortgages, shows your loan-to-value, lets you model a higher rate when a fixed deal ends, and shows how much time and interest monthly or one-off overpayments could save. A year-by-year table and balance chart show exactly how the debt falls. Everything is calculated in your browser, and nothing you type is stored or sent anywhere.

How to use the Mortgage calculator

1. 1 Enter the price and your depositType the property price, then your deposit as a pound amount or as a percentage. The calculator works out the loan amount and your loan-to-value straight away.
2. 2 Set the term and interest rateEnter the mortgage term in years and the interest rate from the deal you are looking at, then choose repayment or interest-only.
3. 3 Add a rate change if you are fixingTick the rate change box, enter how long the deal is fixed for and the rate you expect afterwards, such as the lender's standard variable rate.
4. 4 Try some overpaymentsAdd an extra monthly amount or a one-off lump sum to see how much sooner you could be mortgage-free and how much interest you could save.
5. 5 Check the schedule and save itRead the year-by-year table and balance chart, then copy a summary or download the schedule as a CSV to open in Excel or Google Sheets.

How mortgage repayments are calculated

A repayment mortgage is an amortising loan. Each month you pay the same amount while the rate stays the same, and that payment covers the interest charged that month plus a slice of the loan itself, known as capital. In the early years most of each payment is interest, because the balance is at its highest. As the balance falls, less interest is charged, so more of the same payment goes towards the capital. That is why the balance line in the chart curves rather than falling in a straight line.

The calculator uses the standard annuity formula with interest worked out monthly: the annual rate divided by 12 is applied to the outstanding balance each month. Many UK lenders calculate interest daily or monthly, and some add fees to the loan, so your lender's illustration may differ by a few pounds. It is close enough to compare deals, test what you can afford and plan overpayments, but always rely on the lender's official illustration before you commit.

Repayment or interest-only

With a repayment mortgage you clear the whole loan by the end of the term, as long as you keep up the payments. With an interest-only mortgage you only pay the interest each month, so the payment is lower, but the full amount you borrowed is still owed at the end. You need a credible plan to repay it, such as savings, investments or selling the property, and lenders will want to see that plan before they agree.

Switch between the two options to see the difference. On interest-only the balance chart stays flat and the calculator shows the amount still owed at the end of the term. The total repaid includes that final lump sum, so you can compare the true cost of each option rather than just the monthly figure. Overpayments on an interest-only mortgage reduce the balance you owe at the end, and the calculator shows that new figure.

Loan-to-value and why your deposit matters

Loan-to-value, or LTV, is the mortgage as a percentage of the property's value. Borrowing £270,000 on a £300,000 home is 90% LTV, with a 10% deposit. Lenders usually price their deals in LTV bands, so a lower LTV tends to unlock lower rates. The calculator tells you how much more deposit you would need to reach the next common band, such as 85%, 75% or 60%.

A bigger deposit therefore helps twice: you borrow less, and you may qualify for a cheaper rate. Run the numbers at two deposit levels with the rates you have been quoted for each band to see what the extra savings would really be worth each month and over the term.

• Bands lenders often use include 95%, 90%, 85%, 80%, 75% and 60% LTV, but each lender sets its own.
• LTV is based on the lender's valuation, which can be lower than the price you agreed to pay.
• When you remortgage, your LTV is based on the balance left and the current value, so paying down the loan or a rise in value can move you into a cheaper band.

Fixed rates and what happens when the deal ends

Most UK borrowers choose a fixed rate for two, three, five or more years. When it ends, the mortgage usually moves to the lender's standard variable rate, which is often higher, unless you switch to a new deal. Tick the rate change option, enter the length of the fixed period and the rate you expect after it, and the calculator recalculates the monthly payment on the balance left when the deal ends, spread over the remaining term.

This is useful for stress-testing your budget. Try a follow-on rate a couple of percentage points above today's deal to see whether the payments would still be manageable. In practice most people remortgage before the deal ends, but nobody knows what rates will be available then, so it is sensible to know how a rise would feel.

Overpayments: how much they can save

Paying more than you have to reduces the balance faster, so less interest is charged from then on. In this calculator, overpayments keep your normal monthly payment the same and take the extra off the balance, so the mortgage ends sooner. The results show the time saved and the interest saved compared with paying only the normal amount. Even modest regular overpayments early in the term can cut years off a mortgage, because each pound repaid early stops attracting interest for the rest of the term.

Check your mortgage terms before you overpay. Many fixed and discounted deals allow penalty-free overpayments up to a limit, often 10% of the balance each year, and charge an early repayment charge above that. Some lenders reduce your monthly payment after an overpayment instead of shortening the term, so ask which they do. It is also worth comparing overpaying with keeping an emergency fund and paying off more expensive debts, such as credit cards, first.

What this calculator does not include

The results cover the mortgage itself. They do not include arrangement or product fees, valuation and legal costs, Stamp Duty Land Tax or its equivalents in Scotland and Wales, broker fees, buildings insurance or life cover. Add those to your budget separately, and remember that a deal with a low rate and a high fee can cost more overall than a slightly higher rate with no fee, especially on smaller loans.

Being able to afford the payments on paper is not the same as being offered the loan. Lenders run their own affordability checks based on your income, outgoings, debts and credit history, and test whether you could still pay if rates rose. They usually limit borrowing to a multiple of income too. Use this tool to understand the numbers, then speak to a lender or a qualified mortgage adviser for a decision in principle and advice about your circumstances. This calculator is for illustration only and is not financial advice.

Examples you can copy

Property price     £300,000
Deposit            £30,000 (10%)
Loan               £270,000  ->  90% LTV
Term               25 years
Rate               4.5%

Monthly payment    about £1,500.75
Total interest     about £180,200
Total repaid       about £450,200

M = P × i ÷ (1 − (1 + i)^−n)

P = amount borrowed
i = annual rate ÷ 12 ÷ 100 (monthly rate)
n = number of monthly payments

Interest-only: M = P × i  (P is still owed at the end)

Common mistakes to avoid

Frequently asked questions