Mortgage Calculator UK

Buying a home in the UK involves more than working out the difference between the property price and your deposit. You also need to understand the monthly mortgage commitment, the effect of your interest rate and term, and the cash you will need for costs such as Stamp Duty and conveyancing.

Use this UK mortgage calculator to estimate your monthly repayment, compare it with an interest-only payment, and see how your deposit affects your loan-to-value (LTV). Enter a property price in pounds, adjust the deposit, interest rate and mortgage term, and compare different borrowing scenarios before deciding what you can comfortably afford.

The figures are estimates based on the information entered. A lender’s actual offer and monthly payment may differ depending on its mortgage product, fees, assessment and terms.

How to Calculate Your Mortgage Payments

Start with the property you are considering, rather than the maximum amount you hope to borrow. This makes it easier to see whether the mortgage could fit your monthly budget.

1. Enter the property purchase price. Use the expected price of the house or flat in pounds sterling. For example, enter £300,000 for a property listed at that price.

2. Add your deposit. Enter the cash you expect to put towards the purchase. On a £300,000 property, a £45,000 deposit means you would need to borrow £255,000.

3. Enter the annual interest rate. If you have a mortgage illustration, use the rate quoted by the lender. Otherwise, try a few rates to compare possible payments.

4. Choose the mortgage term. This is the period over which you plan to repay the loan, such as 25 or 30 years.

5. Compare the results. Review the estimated monthly repayment, interest-only payment, LTV and Stamp Duty estimate. Change one input at a time to understand what makes the biggest difference.

If you are still saving for a deposit, run the calculation more than once. Comparing a 10% deposit with a 15% or 20% deposit can help you decide whether saving for longer might make a meaningful difference to the mortgage you need.

Example: Monthly Payments on a £300,000 House

Suppose you are buying a £300,000 home, have saved £45,000 for the deposit and are considering a repayment mortgage at an assumed annual interest rate of 5% over 25 years.

The repayment figure assumes monthly payments, a constant 5% annual rate and a standard capital-and-interest mortgage. Actual lender calculations may vary slightly.

The two monthly figures represent different arrangements. With a repayment mortgage, each payment covers interest and pays down some of the £255,000 borrowed. With an interest-only mortgage, the monthly payment covers the interest, but the original loan remains outstanding unless you repay the capital separately.

The monthly mortgage payment is only one part of the budget for buying a home. You may also need money for Stamp Duty or the relevant devolved property tax, legal work, surveys, moving costs and any mortgage product fees.

Stamp Duty note: the amount depends on the property’s location and the buyer’s circumstances. The tax calculation must distinguish between a standard purchase, an eligible first-time buyer purchase and a purchase subject to higher rates. See the Stamp Duty section below before relying on a tax estimate.

How Your Deposit Changes Your Mortgage

Your deposit determines how much of the purchase price you need to borrow. A larger deposit reduces the loan, which normally lowers the monthly repayment if the interest rate and term stay the same. It can also put you in a different loan-to-value band when comparing mortgage deals.

For a £300,000 property, consider these illustrative repayment estimates at 5% over 25 years:

These figures are rounded estimates calculated using the same rate and term. They illustrate the effect of borrowing less; they are not quotes for specific mortgage products.

The difference between a 5% and a 20% deposit is not just the amount of cash you put down. It also changes the size of the mortgage and may affect the rates available to you. Lenders use LTV alongside other factors, including income, outgoings, credit history and their lending criteria, so a lower LTV does not guarantee approval or a particular rate.

There is another consideration: the deposit is not the only cash you need to complete a purchase. Before committing all your savings, allow for legal costs, moving expenses, property repairs and a reserve for unexpected bills.

Should You Choose a 25-Year or 35-Year Mortgage?

A longer mortgage term spreads the loan over more monthly payments. That usually reduces the amount due each month, but it also means you pay interest for longer.

For the same £255,000 mortgage at a constant 5% annual rate, the approximate repayment comparison is:

A 35-year term makes the monthly payment lower than a 25-year term in this example. However, if the rate remained at 5% throughout, the longer term would result in more interest being paid over the life of the loan.

That trade-off matters if you are deciding between a payment that feels manageable today and a mortgage that you want to clear sooner. A shorter term may reduce the total interest bill but leave less room in your monthly budget. A longer term may give you more breathing space each month, while extending the time you remain in debt.

The term available to you may also depend on the lender’s criteria and your circumstances, including your age. Use the calculator to compare the figures, then check the total cost and conditions of the actual mortgage deals available to you.

Repayment vs Interest-Only Mortgage: What’s the Difference?

The calculator shows both a repayment figure and an interest-only figure because they describe two different ways of paying a mortgage.

Repayment mortgage: each monthly payment covers the interest due and pays back part of the amount borrowed. Provided you make the required payments and the mortgage terms remain as agreed, the loan is scheduled to be cleared by the end of the term.

Interest-only mortgage: your monthly payment covers the interest charged on the loan. You still need a separate, credible plan to repay the original amount borrowed when the mortgage term ends. Interest-only mortgages are less widely available and are generally offered only to borrowers who meet the lender’s criteria.

For example, on a £255,000 loan at 5%, the estimated interest-only payment is £1,062.50 a month. That is lower than the repayment estimate of £1,490.72, but it does not mean the loan is being paid off at the same rate. The £255,000 capital would still need to be repaid.

When comparing these options, do not choose solely on the smaller monthly figure. Consider how the capital will be repaid, what the lender requires and whether the arrangement suits your circumstances.

What Is Loan-to-Value (LTV)?

Loan-to-value, usually shortened to LTV, is the mortgage amount expressed as a percentage of the property’s value. It helps you understand how much of the purchase price you are borrowing.

For example, if you buy a £300,000 property with a £45,000 deposit, you need a £255,000 mortgage.

LTV = mortgage amount ÷ property value × 100

In this example, £255,000 divided by £300,000 gives an LTV of 85%. The remaining 15% is covered by your deposit.

LTV is useful when comparing mortgage deals because lenders often group products into LTV bands. A buyer borrowing 95% of a property’s value may have different options from someone borrowing 80%. The interest rate and eligibility still depend on the lender’s criteria and the rest of your application.

Remember that a lender may use its own property valuation when deciding how much it is prepared to lend. If that valuation is lower than the agreed purchase price, you may need a larger deposit to cover the difference.

How Much Stamp Duty Could You Pay on a UK Property?

Stamp Duty is an upfront purchase cost, not part of your monthly mortgage repayment. The relevant tax depends on where the property is located:

• England and Northern Ireland: Stamp Duty Land Tax (SDLT).

• Scotland: Land and Buildings Transaction Tax (LBTT).

• Wales: Land Transaction Tax (LTT).

The rules and thresholds are not identical across the UK. The amount can also depend on whether you are buying your first home, already own another property, qualify for relief or meet other conditions.

For example, under the current standard residential SDLT rates in England and Northern Ireland, a £300,000 purchase by someone who does not qualify for first-time buyer relief and will own only one residential property attracts £5,000 in SDLT. An eligible first-time buyer purchasing a property for £300,000 may qualify for relief and pay no SDLT. Someone buying an additional property may face higher rates.

Check the official guidance before relying on a figure:

• HMRC: residential Stamp Duty Land Tax rates

• HMRC: Stamp Duty Land Tax overview and other UK property taxes

Important: this calculator’s SDLT result should be treated as an estimate only if its assumptions match your circumstances. If the calculator does not account for first-time buyer relief, higher rates on additional properties, non-resident surcharges or the separate rules in Scotland and Wales, use the relevant official tax calculator or guidance to check the amount due. Do not assume that one SDLT figure applies to every UK buyer.

Other Costs to Budget for When Buying a Home

A mortgage payment can look manageable on its own but feel quite different once the other costs of owning a property are included. Before deciding what you can afford, allow for expenses such as:

• Conveyancing and solicitor fees: legal work involved in transferring ownership and completing the purchase.

• Survey and valuation costs: depending on the survey you choose and the lender’s requirements.

• Mortgage fees: arrangement, booking or other product fees, where applicable.

• Stamp Duty or the relevant property tax: based on the property’s location and your circumstances.

• Buildings insurance: check what your lender requires and whether the property is leasehold or freehold.

• Council Tax and household bills: ongoing costs that sit alongside the mortgage.

• Maintenance and repairs: particularly important if you are buying an older property.

• Leasehold charges: service charges and any ground rent that applies to the property.

For a flat, check the lease terms and service charge history rather than treating the mortgage payment as the whole housing cost. For a house, allow room for repairs and maintenance that might not be obvious during a viewing.

A useful final check is to subtract your estimated mortgage payment and other regular housing costs from your take-home income. The remaining amount should still leave room for food, transport, existing debt repayments, savings and unexpected expenses.

What If Your Mortgage Interest Rate Goes Up?

The rate you enter has a direct effect on the monthly repayment. If you are comparing mortgage deals or planning for the end of a fixed-rate period, try a few different rates rather than relying on one estimate.

For example, on a £255,000 repayment mortgage over 25 years, approximate monthly repayments are:

The estimates assume the rate stays constant throughout the selected term. They are not predictions of future interest rates or offers from lenders.

A fixed-rate mortgage keeps the agreed rate for a set period, while a variable-rate mortgage can change under the product’s terms. When a fixed deal ends, your payment may increase or decrease depending on the rate and product you move to.

If a higher payment would put pressure on your budget, test that scenario before committing to a property. A mortgage that works only at the lowest rate you have seen may leave little room for changes later.

How We Calculate Your Mortgage Repayment

For a standard repayment mortgage, the calculator uses the amount borrowed, the monthly interest rate and the total number of monthly payments to estimate the payment needed to repay the loan over the selected term.

The standard repayment formula is:

M = P × [r(1 + r)ⁿ] ÷ [(1 + r)ⁿ − 1]

Where:

• M is the estimated monthly repayment.

• P is the mortgage amount after subtracting the deposit from the purchase price.

• r is the monthly interest rate, calculated from the annual rate.

• n is the number of monthly payments over the mortgage term.

For an interest-only mortgage, the estimated monthly payment is the outstanding loan multiplied by the monthly interest rate. This payment covers interest only; it does not reduce the capital borrowed.

These formulas provide estimates using the rate entered. They do not automatically account for every lender fee, product condition, future rate change or individual lending decision. The calculator is useful for comparing scenarios, but it does not replace a mortgage illustration or a formal affordability assessment.