Mortgage Calculator UK
Adjust the inputs below. Results update as you type.
How it works
UK mortgages use monthly compounding (monthly rate = annual rate / 12). Standard repayment: payment = PV × r(1+r)^n / ((1+r)^n − 1). Interest-only: payment = PV × monthly rate. Stamp Duty Land Tax (SDLT) applies in England: 0% to £250k, 5% to £925k, 10% to £1.5M, 12% above. First-time buyers have higher exemptions. Scottish LBTT and Welsh LTT use different bands.
Input guidance
- Use realistic rates from lender or provider quotes instead of headline averages.
- Model conservative, baseline, and optimistic scenarios before deciding.
- Include recurring real-world costs (fees, taxes, insurance, maintenance) where relevant.
The formula
UK repayment mortgages amortize with M = P · r · (1+r)^n / ((1+r)^n − 1). Many UK deals are fixed for 2–5 years then revert to the lender's standard variable rate.
Worked example
A £250,000 repayment mortgage at 5% over 25 years costs about £1,461/month. Interest-only versions pay just the interest, leaving the full capital due at the end.
More examples to test
- Conservative case: use a higher interest rate and lower growth assumptions to stress-test affordability.
- Optimistic case: use a lower rate with stable income assumptions to compare upside potential.
How to interpret results
Treat this as a planning model, not a final approval tool. Compare at least two scenarios and focus on total-cost and cash-flow trade-offs.
When this can be inaccurate
Results can diverge due to fees, changing rates, tax rules, lender policies, and behavior changes that simplified models cannot fully capture.
Change history
- July 2026: Quality-reviewed for publication with formula checks and explanatory copy updates.
Site-wide corrections also appear on the corrections log.
Compare mortgage and refinance offers
Rates vary by lender, profile, and market conditions.
Compare top personal finance offers
Offers and rates vary by eligibility.
Frequently asked questions
Repayment or interest-only?+
Repayment mortgages clear the balance by the end of the term; interest-only keeps payments low but the full capital must be repaid separately at the end.
What is the SVR?+
The standard variable rate a mortgage reverts to after a fixed or tracker deal ends. It is usually higher, so many borrowers remortgage before then.
What is stamp duty?+
A UK tax on property purchases above certain thresholds, separate from the mortgage but a major upfront cost to budget for.
How should I use this result?+
Treat it as a planning estimate. Compare at least two realistic scenarios, then confirm with statements, quotes, or a qualified professional before acting.
How often should I refresh assumptions?+
Refresh whenever rates, income, costs, or policy limits change materially, and before making irreversible commitments.