--- title: "UK mortgage calculator with Stamp Duty estimate | AumnI tools" description: "Work out the monthly payment on a UK repayment mortgage over 25 years, add a Stamp Duty Land Tax estimate for England, and see how overpayments cut the interest." url: https://aumnitools.com/uk/tool/mortgage-calculator category: "Financial" country: "United Kingdom" updated: 2026-11-08 --- # Mortgage Calculator Most UK repayment mortgages are quoted over 25 years, and the deposit you save is only part of the cash you need on completion. This calculator turns a price, deposit, rate and term into a monthly payment and a full schedule, and can add a Stamp Duty Land Tax estimate with or without first-time buyer relief. ## United Kingdom rules and figures - Stamp Duty Land Tax in England and Northern Ireland is 0% up to £125,000, 2% from £125,000 to £250,000, 5% to £925,000, 10% to £1.5 million and 12% above that. - First-time buyer relief charges 0% up to £300,000 and 5% on the part from £300,000 to £500,000. It is not available when the price is over £500,000. - Buyers who already own another home usually pay 5% extra Stamp Duty, and non-UK residents usually pay 2% extra, on top of the standard rates. - Scotland charges Land and Buildings Transaction Tax and Wales charges Land Transaction Tax. Both have their own bands, so the estimate here does not apply there. - No national minimum deposit is built in; each lender sets its own. The 25-year starting term is a tool default rather than a legal limit. - GOV.UK does not state an effective date on its Stamp Duty rates page, so the bands were treated as current on the date they were checked. Sources: [GOV.UK: Stamp Duty Land Tax residential property rates](https://www.gov.uk/stamp-duty-land-tax/residential-property-rates) (checked 2026-11-08); [Welsh Government: Land Transaction Tax differences to SDLT](https://www.gov.wales/land-transaction-tax-differences-stamp-duty-land-tax) (checked 2026-11-08); [GOV.UK: SDLT Welsh transactions](https://www.gov.uk/guidance/stamp-duty-land-tax-welsh-transactions) (checked 2026-11-08); [Revenue Scotland: LBTT legislation guidance](https://revenue.scot/taxes/land-buildings-transaction-tax/lbtt-legislation-guidance) (checked 2026-11-08) ## How the mortgage calculator works The loan is the price minus your deposit. Interest is charged each month at one twelfth of the annual rate on what you still owe, and the fixed monthly payment is set so the balance reaches zero at the end of the term. An overpayment goes straight off the balance, so the loan ends sooner and less interest is charged. Formula: `monthly payment = loan × m × (1 + m)^months ÷ ((1 + m)^months − 1), with m equal to the yearly rate divided by 12` - The term starts at 25 years, the usual length for a UK repayment mortgage in this tool. Type your own term to change it. - Council Tax and the service charge and ground rent on a flat or leasehold home are entered as running costs and spread across the months. - Tick the Stamp Duty box to estimate the tax for England and Northern Ireland; the cash needed up front is the deposit plus that tax. - One rate is used for the whole term, so a fixed period followed by a lender's standard variable rate is not modelled. - Only a repayment loan is calculated; an interest-only mortgage would leave the whole loan outstanding at the end. ## How to use the mortgage calculator 1. **Enter the price and your deposit.** Type the purchase price and the cash you will put down. The loan is the difference, and the deposit is also shown as a share of the price. 2. **Set the term and rate.** Enter the term in years and the interest rate from your offer. The term starts at 25 years. 3. **Add running costs.** Open the extra costs to include Council Tax, home insurance and any service charge and ground rent. 4. **Estimate Stamp Duty.** Tick the first-time buyer box if it applies. Relief is applied only when the price is within the limit; above it the standard bands are used. 5. **Test an overpayment.** Enter a monthly overpayment to see the earlier payoff date and the interest saved against the plain schedule. ## Example: A £350,000 home with a 10% deposit at 4.5% over 25 years A £35,000 deposit leaves a loan of £315,000, so the repayment is £1,750.87 a month and total interest is £210,261.69. Stamp Duty on £350,000 is £7,500 for a standard buyer, or £2,500 with first-time buyer relief, so the cash needed on completion is £42,500 or £37,500. Overpaying £200 a month ends the mortgage after 249 payments instead of 300 and cuts the interest to £169,792.64, a saving of £40,469.06. ## When to use the mortgage calculator - **Comparing two mortgage offers.** Enter the rate and term from each offer to check the monthly repayment before looking at fees. - **Budgeting for completion day.** Add the Stamp Duty estimate to your deposit to see the cash needed, with and without first-time buyer relief. - **Planning overpayments.** Try a monthly overpayment to see how many years come off the term and how much interest is saved. - **Choosing a term.** Compare 25 years with a longer or shorter term to see how the payment and the total interest trade off. ## What the mortgage calculator does not do - Stamp Duty is estimated for a single main home in England and Northern Ireland only. Higher rates for additional homes and for non-UK residents, and Scottish and Welsh taxes, are not calculated. - One interest rate applies for the full term. Introductory fixed rates that revert to a different rate are not modelled. - Mortgage insurance is not modelled, because no UK rule for it was checked, and lender fees, valuation and legal costs are not part of the payment. - Interest-only and part-and-part mortgages are not supported, and Council Tax and service charges stay constant for the whole term. - The Affordability tab applies an American 28/36 rule for a rough budget; UK lenders work from their own income multiples and checks. ## When something else is a better fit - **When you already have a mortgage and want to test overpaying it**, use the [Early Payoff Calculator](https://aumnitools.com/tool/early-payoff-calculator.md), which starts from your current balance. - **When you want several loans side by side**, use the [Loan Comparison Tool](https://aumnitools.com/tool/loan-comparison-tool.md). - **When you need the exact figures for a real offer**, use the illustration your lender provides, which includes its own fees and rate rules. ## Questions about the mortgage calculator ### How much is the monthly payment on a £315,000 mortgage? At 4.5% over 25 years the repayment is £1,750.87 a month, with £210,261.69 of interest over the term. A 20% deposit on the same £350,000 price lowers the loan to £280,000 and the payment to £1,556.33. ### How much Stamp Duty do I pay on £350,000? A standard buyer in England or Northern Ireland pays £7,500: nothing on the first £125,000, 2% on the next £125,000 and 5% on the last £100,000. A first-time buyer pays £2,500, which is 5% of the £50,000 above £300,000. ### Does first-time buyer relief apply at any price? No. It applies only up to £500,000. Over that price the standard bands are used on the whole price, and the calculator shows a message saying so. ### Does this work for Scotland or Wales? The payment calculation does, but the tax estimate does not. Scotland charges Land and Buildings Transaction Tax and Wales charges Land Transaction Tax, each with its own bands. ### What does a £200 monthly overpayment save? On the example loan it ends the mortgage after 249 payments, about 20 years and 9 months, and cuts interest by £40,469.06. Check your lender's overpayment limits first, because some charge for large ones. ## Related tools - [Early Payoff Calculator](https://aumnitools.com/tool/early-payoff-calculator.md): Shows how much time and interest an extra monthly payment saves on a loan - [Loan Comparison Tool](https://aumnitools.com/tool/loan-comparison-tool.md): Compares loan offers side by side on monthly payment, total interest and total cost - [Budget Planner](https://aumnitools.com/tool/budget-planner.md): Plans monthly income and expenses by category, with a health score and debt payoff ## About this page Runs in your browser: what you enter is processed on this device and is not uploaded. Estimates for planning only, not financial, tax or legal advice. Check figures that matter with a qualified professional. Last checked against the tool's code on 2026-11-08. Interactive version: https://aumnitools.com/uk/tool/mortgage-calculator