Mortgage Calculator
Estimate your monthly payment, total interest, and repayment schedule.
- Loan amount
- £270,000.00
- Monthly payment
- £1,500.75
- Total interest
- £180,223.69
- Total repaid
- £450,223.69
Calculator guide
How this mortgage works
A repayment mortgage uses a fixed monthly payment calculated so the balance reaches exactly zero at the end of the term — this calculator uses that same standard amortization formula, based on the loan amount (property price minus deposit), the interest rate, and the term in years. Each payment is split between interest (charged on whatever balance remains) and principal (which reduces the balance) — early payments are mostly interest, and that split gradually reverses over the term.
An interest-only mortgage only pays the interest each month — the balance never reduces, and the full amount borrowed is still due at the end of the term, usually repaid by selling the property, an investment vehicle, or refinancing. This calculator supports both: switch the repayment type to compare the monthly cost directly.
Worked example: a £270,000 loan (£300,000 property, 10% deposit) at 4.5% over 25 years comes to roughly £1,500 a month on repayment terms, with total interest of around £180,000 over the full 25 years — the calculator's own full breakdown updates live as you change any of the inputs.
Planning to pay extra? Open the mortgage overpayment calculator.
Methodology and sources
Last reviewed:
Repayment results use the standard monthly amortization formula: the loan principal is the property price minus the deposit, the annual interest rate is divided into a monthly rate, and the fixed monthly payment is the amount that repays the balance over the selected term.
Interest-only results multiply the outstanding loan by the monthly rate and do not reduce principal during the term. The amortization table is generated from the same monthly balance calculation used for the headline payment.
Assumptions
- Interest rate is assumed to stay constant for the full term entered.
- Arrangement fees, valuation fees, early repayment charges, insurance, tax, and affordability checks are not included.
- Results are rounded for display and are estimates for comparison, not a mortgage offer.
Mortgage results are illustrative only. Lenders assess affordability, fees, product terms, and eligibility separately.
Spot a methodology issue? Send a correction.
Frequently asked questions
What is loan-to-value (LTV) and why does it matter?
LTV is the mortgage amount as a percentage of the property price — a £270,000 mortgage on a £300,000 property is 90% LTV. Lower LTV (bigger deposit) usually qualifies for better interest rates, since it's less risk for the lender.
Does this calculator include fees or overpayments?
No — it estimates the interest and repayment schedule from the property price, deposit, rate, and term only. Arrangement fees, valuation fees, and the effect of overpayments are not modelled.
Why is the monthly payment the same every month, but the interest changes?
The payment amount is fixed by design, but it's split differently each month: interest is calculated on whatever balance remains, so as the balance shrinks, less of each fixed payment goes to interest and more goes to principal.
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