UK Mortgage Repayment Calculator

Compare a capital-repayment mortgage with interest-only on the same sterling loan. Default term is 25 years — the common UK planning period — not the 30-year US product on our PITI mortgage calculator.

Rate is whatever you type — this is not a live lender quote. Fees, product rate type (fixed, tracker, SVR) and overpayments are outside this estimate.

How this calculator differs from the US PITI page

The job on this page is a UK capital-repayment or interest-only estimate. The job on the US mortgage calculator is principal, interest, property tax and homeowners insurance (PITI), with a 30-year default and a PMI discussion. Those are different products. Merging them would hide the answer that actually changes.

  • Term. 25 years is the default here. UK lenders also offer longer terms; use the selector. Do not assume 30 years.
  • Repayment vs interest-only. Switching the product changes whether the balance falls to zero.
  • No PMI line. UK high-LTV cost usually sits in the rate, not a separate US-style PMI premium.
  • Purchase costs sit outside the monthly figure. Stamp Duty Land Tax, conveyancing, and broker fees are not mortgage instalments.

Formula

Capital repayment uses standard fixed-rate amortisation, the same mathematics banks use for a repayment mortgage:

M = P × [ i(1+i)^n ] / [ (1+i)^n − 1 ]
M = monthly repayment · P = loan · i = monthly rate · n = number of months

Interest-only is M = P × (annual rate / 12). The original loan is still due at the end unless you have a separate repayment vehicle. This page does not model that vehicle.

By Suhaib Hassan · Formula verified 18 Sep 2026 · Method v2.2-UK · How CalculatePilot verifies formulas

A worked sterling example (pre-computed)

Property £300,000 · deposit £30,000 (10%) · loan £270,000 · rate 4.5% · term 25 years (300 payments). Figures use the same formula as the calculator, so the answer is readable if JavaScript is off.

Repayment, 25 years
Monthly payment ≈ £1,500.75
Total repaid ≈ £450,224
Interest ≈ £180,224
Balance at the end = £0

Interest-only, same loan
Monthly payment ≈ £1,012.50
Interest over 25 years ≈ £303,750 if the rate never changes
Balance still due at the end = £270,000

Interest-only is cheaper each month and more expensive as a lifetime cost unless the £270,000 is repaid some other way. That trade-off is why this page is not a currency overlay of the US calculator.

What this monthly figure does not include

  • Stamp Duty Land Tax (England and Northern Ireland) — a one-off purchase cost. Use the UK Stamp Duty Calculator for the 1 April 2025 residential bands, then confirm on GOV.UK.
  • Land Transaction Tax / Land and Buildings Transaction Tax — Wales and Scotland use different regimes.
  • Council tax, buildings insurance, ground rent, service charge — household costs, not lender repayment.
  • Product fees added to the loan, early-repayment charges, or a rate switch from fixed to SVR.

For a regulated view of affordability, start with MoneyHelper’s mortgage calculators, then confirm with a lender quote.

Who should use the other mortgage page instead

  • Anyone modelling US property tax plus homeowners insurance inside the monthly housing cost — that is the PITI calculator.
  • Anyone who needs a full principal schedule — amortisation.
  • Anyone testing whether a new rate beats the current loan after fees — refinance breakeven.

Frequently asked questions

Why is the default term 25 years, not 30?

A 25-year term is still a common UK planning default. Many UK lenders also offer 30, 35 or 40 years depending on age and affordability. Change the selector. The US PITI calculator defaults to 30 years because that is the common US product.

What is the difference between repayment and interest-only?

Repayment pays down the loan each month. Interest-only pays only interest; the original loan is still due at the end unless you have a separate repayment vehicle.

Does this include Stamp Duty Land Tax?

No. SDLT is a one-off purchase cost. Use the UK Stamp Duty Calculator for current England and NI residential bands.

Is PMI part of a UK mortgage payment?

No. PMI is a US product. In the UK a high loan-to-value ratio usually means a higher interest rate, not a separate PMI line.

Are these figures a lender offer?

No. This is a planning estimate. Confirm with a regulated adviser or lender.

Next calculation

1. Work out Stamp Duty (England & NI) → 2. Work out LBTT if the home is in Scotland → 3. Work out LTT if the home is in Wales → 2. Model a monthly overpayment on this loan → 3. Model US-style PITI if that is the product → 4. Test a remortgage after fees →

Read the judgement layer in the mortgage payment guide if you want the term decision in words.

Estimate only. UK repayment / interest-only · method v2.2-UK · last verified 18 Sep 2026 · sources and verification · who builds CalculatePilot