Calculate your UK mortgage monthly payment, total interest, and upfront cash needed including Stamp Duty (SDLT). Standard repayment mortgage math at any term + interest rate. Handles first-time buyer SDLT relief and the +5% additional-property surcharge.
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£
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Monthly payment
£0
Loan amount
£0
LTV
0%
Total interest
£0
Upfront cash needed
Deposit
£0
Stamp Duty (SDLT)
£0
Total upfront
£0
Plus solicitor fees (~£1-2k), survey (~£300-£1.5k), mortgage arrangement fees (~£0-£2k), and removal costs.
How the monthly payment is calculated
Standard amortising repayment mortgage formula: M = P × r × (1+r)ⁿ / ((1+r)ⁿ − 1), where P is the loan amount, r is the monthly rate (annual ÷ 12), and n is the number of months (term × 12). Every UK lender uses this. The first months are mostly interest; you pay down the principal slowly at the start, fast at the end.
Upfront cash beyond the deposit
A common surprise for first-time buyers: the deposit isn't the only upfront cash you need. SDLT (when applicable) can be substantial — at £500k, even with first-time buyer relief, it's £10,000. Add solicitor fees, surveys, arrangement fees, removal costs — easily another £3k-£5k. This calculator includes SDLT in the upfront-cash figure; budget more for the rest.
The standard UK residential mortgage term is 25 years (vs 30 in the US). Some lenders offer up to 35 or 40 years, particularly for younger borrowers — useful for keeping monthly payments down at the cost of meaningfully more total interest. Shorter terms (10-15 years) get you out of debt faster but require higher monthly payments.
How does the LTV (loan-to-value) ratio affect my rate?
LTV bands typically determine the rate band: 60% (lots of equity) gets the best rates, 75% a small markup, 85% noticeable markup, 90% meaningful markup, 95% the highest rates available (and not all lenders offer 95% LTV). A bigger deposit, even a small step from 91% LTV to 89% LTV, can save thousands over the term.
What's a fixed-rate period?
UK mortgages don't typically fix the rate for the whole term — instead, you fix for an initial period (2 or 5 years most commonly), then the loan reverts to the lender's Standard Variable Rate (SVR) unless you remortgage. The SVR is usually 2-4 percentage points higher than competitive fixed-rate deals, so most borrowers remortgage at the end of each fixed period. This calculator uses a single rate for the whole term as a simplification — useful for comparing scenarios but a real mortgage offer will show explicit initial vs SVR periods.
What other costs come with buying a house in the UK?
Beyond deposit and SDLT: solicitor / conveyancing fees (~£1,000-£2,000), survey (~£300-£1,500 depending on type — homebuyer report, building survey), mortgage arrangement fee (~£0-£2,000, often added to the loan), valuation fee (sometimes free), Land Registry fees (~£200-£300), and removal costs (£500-£3,000). Budget another £2k-£5k beyond deposit + SDLT.
Should I overpay my mortgage?
Most fixed-rate mortgages allow up to 10% overpayment per year without penalty. Overpayment shortens the term and reduces total interest, but only makes sense if (a) your rate exceeds what you'd earn investing the same money, after tax, and (b) you have an emergency fund + maxed ISA / pension already. With current rates at ~5%, overpayment beats most cash savings and many fixed-income investments — but a long-term equity ISA may still win for higher-risk-tolerance borrowers.
Is this calculator accurate?
Monthly payments use the standard amortising mortgage formula (M = P·r·(1+r)ⁿ / ((1+r)ⁿ − 1)) — identical to what every UK lender uses. SDLT applies the rates effective from 1 April 2025 (unchanged for FY 2026-27). What it does NOT model: fixed-rate vs SVR phases, mortgage arrangement fees, valuation fees, solicitor fees, or the specific lender's product-fee handling. For an actual mortgage decision, get an in-principle offer that shows the lender's exact APRC.