Mortgage Calculator
Calculate monthly repayments, total interest, and cost of borrowing for any UK mortgage.
Common questions
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What is a mortgage repayment calculator?
A mortgage repayment calculator works out the monthly payment you would owe on a given home loan. Enter the purchase price, deposit, interest rate, and term length and it applies the standard amortisation formula to give you an instant monthly figure — plus total interest paid over the full term. This tool supports both repayment and interest-only mortgages, shows a year-by-year amortisation schedule, and displays your loan-to-value ratio.
How mortgage repayments are calculated
For a repayment mortgage, the standard formula is:
Where P is the loan principal (purchase price minus deposit), r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments (term years × 12). In early years, most of each payment covers interest. As the balance falls, the split shifts toward capital — this is shown in the amortisation table below the calculator.
For an interest-only mortgage, the monthly payment is simply P × r — you pay only the interest. The full loan balance is due at the end of the term, either from a repayment vehicle (endowment, ISA, pension drawdown) or from selling the property.
Why your mortgage rate matters more than you think
The difference between a 4% and a 5% interest rate on a £250,000 repayment mortgage over 25 years is roughly £33,000 in total interest. That is why comparing lenders and fixing at the right moment is one of the highest-return financial decisions most people make. Use this calculator to model scenarios before talking to a mortgage broker — understanding the numbers puts you in a stronger position.
Key rates to know in 2026: the Bank of England base rate drives the floor for most mortgage pricing. 2-year and 5-year fixed rates are available from major lenders. Tracker mortgages follow the base rate plus a margin. Arrangement fees (typically £500–£1,500) should be added to the total cost when comparing deals.
Integrate into your own product
Free to startA single GET /api/properties/{uprn}/ call returns structured JSON with median sold price for the area, EPC rating, floor area (sqm), council tax band, property type, and comparable sold prices — giving mortgage calculators and affordability tools the real property data needed to pre-populate inputs rather than relying on user estimates.
Structured as JSON · queryable by UPRN or postcode · ready to embed in any application
Exact measurements
Real values — distances, concentrations, counts — not rounded ratings
29M+ UK properties
Every address queryable by UPRN or postcode
REST API
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Mortgage calculator FAQ
How is a mortgage repayment calculated?
M = P × r(1+r)^n / ((1+r)^n − 1), where P = loan, r = monthly rate (annual ÷ 12), n = total months. For interest-only: M = P × r. The calculator above does this instantly.
What is a good mortgage rate in the UK in 2026?
Typical 2-year fixed rates for 25–40% deposit borrowers are 4–5% in 2026. The Bank of England base rate is the key driver. Always compare deals including arrangement fees, not just the headline rate.
How much can I borrow on a mortgage?
Most lenders use 4–4.5× gross annual income. Some go to 5–6× for high earners. Affordability stress tests at 3% above the initial rate are typically the binding constraint.
What is LTV and why does it matter?
LTV (loan-to-value) is the loan as a percentage of the property price. Lower LTV means better rates. Key thresholds: 60%, 75%, 80%, 85%, 90%, and 95%.
Is it worth overpaying my mortgage?
Yes — overpaying reduces your balance faster and cuts total interest paid significantly. Most lenders allow up to 10% of the outstanding balance per year without early repayment charges.
What is an amortisation schedule?
An amortisation schedule shows how each payment splits between interest and capital. Early payments are mostly interest; later payments are mostly capital. The table is generated automatically below the calculator.
What is the difference between repayment and interest-only?
Repayment clears both interest and capital — the loan is fully paid at term end. Interest-only covers only interest monthly; the full capital is due at the end. Interest-only requires a repayment strategy.
Last reviewed: May 2026
Sources: Bank of England — Base Rate · MoneyHelper — Mortgage Calculator · FCA — Mortgages
See also: How do mortgages work? · What property can I afford? · How much deposit do I need?