How much deposit do I need for a UK mortgage?

Most UK lenders require a minimum 5% deposit, but the lowest interest rates are reserved for borrowers with 25% or more. A 15–20% deposit accesses competitive mid-tier rates, 10% is the typical first-time-buyer band, and 5% deals usually carry the highest rates and the strictest affordability checks. Help to Buy, Shared Ownership, and 95% guarantor mortgages exist for buyers who can't reach 10%. Above the deposit itself, budget for Stamp Duty, legal fees, surveys, broker fees, and moving costs — the calculator's Advanced Options model these explicitly so you see the full cash outlay.

What is a repayment mortgage?

A repayment mortgage charges a fixed monthly payment that covers both interest and principal. Each month a slightly larger share goes to principal and a slightly smaller share to interest, so the balance steadily falls to zero at the end of the term. This is the default UK structure for residential owner-occupiers — at term end, you own the property outright. It costs more per month than interest-only but materially less over the full term because you stop paying interest on principal you've already repaid.

What is an interest-only mortgage?

An interest-only mortgage charges a monthly payment that covers only the interest on the loan. The full balance is still owed at term end and must be repaid via a separate "repayment vehicle" — a cash ISA, a stocks-and-shares ISA, a pension, the sale of another property, or an inheritance. Monthly cost is lower, but total cost is higher (you pay interest on the full balance for the entire term) and you carry repayment-strategy risk if the vehicle underperforms. Most UK lenders now require evidence of a credible repayment plan and a minimum equity stake.

How is Stamp Duty calculated?

Stamp Duty Land Tax (SDLT) is a banded tax — different rates apply to different portions of the price. For home movers in England and Northern Ireland: 0% on the first £250,000, 5% on £250,001–£925,000, 10% on £925,001–£1,500,000, and 12% above. First-time buyers pay 0% up to £425,000 and 5% on £425,001–£625,000 (relief lost above £625k). Additional-property and buy-to-let purchases add a 3-percentage-point surcharge across all bands. Companies and corporate buyers pay a flat 17% above £500,000. Scotland uses LBTT and Wales uses LTT — both have different bands not modelled here.

Loan-to-value (LTV) is the ratio of the loan amount to the property price, expressed as a percentage. On a £500,000 property with a £125,000 deposit, the loan is £375,000 so LTV is 75%. UK lenders price mortgages in LTV tiers — typically 60%, 75%, 85%, 90%, and 95%. The lower your LTV, the lower the rate. Crossing a tier downwards at remortgage time (e.g. 81% to 74%) can unlock a much better rate, which is why some borrowers pay a small lump sum at remortgage to drop into a lower tier.

Can I overpay my mortgage?

Yes — most UK lenders allow up to 10% of the outstanding balance per calendar year fee-free. Overpayments reduce the principal directly and therefore cut both the term and the total interest paid. On a £375,000 mortgage at 5% over 25 years, a £200/month overpayment shortens the term by roughly 5 years and saves a meaningful share of the total interest. The repayment tab's overpayment field models this exactly. During a fixed-rate period, check your lender's specific Early Repayment Charge (ERC) rules before exceeding the 10% allowance.

How much can I borrow in the UK?

UK lenders typically cap borrowing at 4.0–4.5× combined gross annual income, with some specialist or professional mortgages allowing up to 5–5.5× for higher earners. The actual cap is then stress-tested against your monthly commitments, existing debts, dependents, and an assumed future rate (usually the offer rate + 2–3 percentage points). The Affordability tab models all of these factors and returns the lower of the income-multiple cap and the DTI-based cap, with a clear Comfortable / Within Reach / Stretched / Unlikely rating.

What costs should I budget for besides repayments?

On top of the monthly mortgage payment, UK homeowners typically pay council tax, buildings and contents insurance, mortgage protection insurance, service charges and ground rent on leasehold flats, and ongoing maintenance. Tick "Include Additional Costs" in the repayment tab to add these to the calculation and see the realistic total monthly out-of-pocket figure. Upfront costs include Stamp Duty, legal fees (£800–£2,000), valuation (£300–£600), broker fees if applicable, and any lender arrangement fee (often £999, sometimes added to the loan).

What is remortgaging?

Remortgaging is switching your mortgage to a new deal — usually with a different lender, sometimes with the same one — at the end of your current fixed-rate period. The goal is to avoid reverting to the lender's higher Standard Variable Rate (SVR). A good time to remortgage is 3–6 months before your fix ends, when LTV has dropped into a better tier, or when interest rates have fallen materially. Compare the new rate plus any product, valuation, legal, and broker fees against staying put — sometimes a higher headline rate with no fees beats a lower rate with £1,500 of fees.

How do lenders assess affordability?

UK lenders run a two-step affordability check. First, they cap the loan at an income multiple — typically 4.0–4.5× combined gross income, less existing debts and commitments. Second, they stress-test the resulting monthly payment against your net take-home pay at a stressed rate (usually the offer rate + 2–3 percentage points) to ensure you could still afford the payment if rates rose. They also review your bank statements for spending patterns, credit file for missed payments, and employment history. The Affordability tab follows the same logic so the maximum borrowing figure it produces is close to what a lender would actually offer.

Mortgage Calculator UK

Calculate UK mortgage repayments, interest-only payments, Stamp Duty, borrowing capacity, and long-term homeownership costs.

Property & Mortgage Details

Enter the price, deposit, term, and rate for your repayment mortgage.

Property Price

Loan Term

years

Mortgage Deposit

A larger deposit reduces LTV and unlocks lower rate tiers.

Interest Rate

Average UK fixed rates 4–6% in 2026

Monthly Take-Home Income (optional)

Used for the UK Mortgage Health Score payment-burden factor only.

Council Tax

per year

Home Insurance

per year

Mortgage Protection Insurance

per year

Service Charges

leasehold flats

Ground Rent

leasehold flats

Maintenance

estimated annual

Other Annual Costs

utilities, etc.

UK Mortgage Calculator

The SamCalculator UK Mortgage Calculator helps prospective buyers, remortgagers, and buy-to-let investors evaluate the full cost of a UK mortgage — not just the headline monthly repayment. The five integrated tools cover everything from a basic repayment schedule to Stamp Duty Land Tax, affordability, interest-only strategy planning, and side-by-side comparison of competing fixed-rate deals.

Built for UK residents, all amounts are in British Pounds (£), dates use the DD/MM/YYYY convention, and tax rules reflect SDLT bands in England and Northern Ireland. Lending multiples follow standard UK affordability practice (typically 4.0–4.5× combined income), with optional adjustments for high-income earners and professional mortgages.

How a UK Mortgage Works

Repayment Mortgage

Each monthly payment covers part interest, part principal. The loan is fully repaid over the term — typically 25 years, though 30- and 35-year terms are increasingly common. This is the default UK structure for residential owner-occupiers.

Interest-Only Mortgage

Monthly payment covers interest only — the full loan balance must be repaid at term end via a separate "repayment vehicle" (ISA, pension, sale of property). Lower monthly cost but materially higher total cost and repayment-strategy risk.

Five Ways to Use This Calculator

1. Repayment
Calculate the monthly cost of a standard repayment mortgage on any property price, deposit, and term.
2. Interest-Only
Compare interest-only against full repayment, with repayment-vehicle projection and shortfall risk.
3. Affordability
Estimate maximum borrowing from combined income, commitments, and deposit using UK lender rules.
4. Stamp Duty
Estimate SDLT for first-time buyers, home movers, additional-property purchases, and corporate buyers.
5. Comparison
Compare up to three competing deals — rates, fees, terms, overpayments — and rank by lowest total cost.
6. Overpayment Planner
Built into the repayment tab — quantify years and interest saved by paying down principal faster.

Best Practices for UK Mortgage Decisions

Aim for at least a 25% deposit to access the lowest fixed-rate tier offered by mainstream lenders.
Keep the loan-to-income ratio below 4.5× and total monthly housing costs below 35% of take-home pay.
Stress-test affordability at a rate 2–3 percentage points above the headline offer.
Compare 2-year, 5-year, and 10-year fixed-rate products against your expected time in the property.
Budget for arrangement fees, valuation, legal costs, broker fees, and Stamp Duty as part of the total upfront cost.
Use overpayments while rates are low — most UK lenders allow 10% of the balance per year fee-free.

Why a UK-Specific Mortgage Calculator Matters

Generic mortgage calculators tend to follow US conventions — monthly compounding, PMI rules, FHA limits — that do not match how UK lenders price and assess loans. UK mortgages use a flat per-month interest convention without compounding the unpaid balance, Stamp Duty is a banded tax rather than a percentage of price, and affordability is governed by income-multiple rules rather than US-style DTI thresholds.

This calculator implements all of the UK-specific rules out of the box. Every figure — repayment, interest-only, SDLT, max borrowing, comparison — is computed using the correct UK methodology so the numbers you see match what your lender would calculate.

Tricky Cases & Edge Cases

First-time buyer above £625,000: Relief is lost entirely — standard home-mover rates apply.
Joint applications with one first-time buyer: Both buyers must be first-time buyers for FTB relief.
Additional-property surcharge: 3% surcharge applies even if it's your only second property.
Interest-only at remortgage: Many lenders require an acceptable repayment strategy and minimum equity.
95% LTV first-time deals: Often require Help to Buy, Shared Ownership, or a parental guarantor.

Core Formulas

Monthly Repayment

M = P × [r × (1+r)ⁿ] ÷ [(1+r)ⁿ − 1]

Where P = loan amount, r = monthly rate (annual ÷ 12), n = total payments (years × 12).

Interest-Only Payment

IO = Loan × Annual Rate ÷ 12

Loan-to-Value (LTV)

LTV = Loan Amount ÷ Property Price × 100

SDLT Banded Tax

SDLT = Σ (Portion in Band × Band Rate)

Common Mistakes

Comparing deals on monthly payment alone — ignore total cost, fees, and early-repayment charges at your peril.
Forgetting Stamp Duty, legal fees, and survey costs in the deposit budget.
Choosing a 35- or 40-year term without modelling how much more interest you'll pay.
Underestimating monthly ownership costs (council tax, insurance, service charge, maintenance).
Assuming interest-only is "cheaper" — total cost is higher, and you need a repayment strategy.

Editorial Standards

All formulas, SDLT bands, affordability rules, and product mechanics on this page have been cross-checked against publicly available UK government and regulator documentation. SamCalculator is independent — we do not receive referral payments from any lender, broker, or estate agent. This page is updated as UK Stamp Duty, lender LTV policies, and affordability rules change.

Mortgage Calculator UK

UK Mortgage Calculator

How a UK Mortgage Works

Five Ways to Use This Calculator

Best Practices for UK Mortgage Decisions

Why a UK-Specific Mortgage Calculator Matters

Tricky Cases & Edge Cases

Core Formulas

Common Mistakes

Editorial Standards

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