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Useful next calculations
Rates & sources
Illustrative monthly payment using the standard annuity formula. The rate is supplied by the user and must be checked against a lender’s personalised illustration.
| Band / figure | Rate |
|---|---|
| Formula | P × r(1+r)ⁿ / ((1+r)ⁿ − 1) |
| Typical UK LTV bands | 60% / 75% / 85% / 95% |
| Rate assumption | entered by you |
| Binding comparison | lender ESIS / illustration |
Source: MoneyHelper — mortgage calculator guidance — check the linked guidance and any live quote before acting.
When to use this calculator
- Before comparing mortgage products, brokers or repayment types.
- When you want to test how a different deposit, rate or term changes the payment.
- When you need a quick estimate before using a formal illustration or agreement in principle.
- When you are stress-testing your budget against a higher rate.
Example: estimating repayments with a 20% deposit
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
| Input | Value |
|---|---|
| Property value | £250,000 |
| Deposit | £50,000 |
| Mortgage required | £200,000 |
| Rate and term | 5.25% over 25 years |
Review the monthly repayment and total interest together. Then increase the rate and shorten the term in separate runs to see whether the budget has enough headroom and whether a higher payment could materially reduce lifetime interest.
How to read your results
Monthly Payment
Estimated monthly mortgage repayment under the rate, term and balance you entered. Compare it with a lender illustration before you apply.
Total Interest
Additional amount paid above the original principal during the term, using the rate you entered. Fees and early-repayment charges are not included unless you added them.
LTV
Loan-to-value is the mortgage as a percentage of the property value. Crossing common LTV bands can change product eligibility and pricing.
Method & assumptionsAuthoritative sources
This calculator works on a standard capital and interest repayment basis, spreading your loan across the chosen term so that each monthly payment reduces the outstanding balance while also covering interest. The calculation uses compound interest applied monthly, which is how most mortgage lenders price their products. The result shows an illustrative monthly payment based on the rate and term you enter — it does not account for mortgage fees added to the loan, payment holidays, or rate changes at the end of a fixed period. Real-world repayments may differ slightly depending on how your lender calculates daily interest. Always request a full Key Facts Illustration (KFI) or European Standardised Information Sheet (ESIS) from any lender before committing.
Common mistakes
- !Mixing up loan amount and property value, which can distort affordability and LTV.
- !Using a headline rate but forgetting fees, insurance, taxes or repayment type.
- !Testing only one term length instead of comparing the payment and total cost together.
- !Forgetting that a repayment mortgage and an interest-only mortgage produce very different monthly figures.
What to do next
- Stress-test the same balance at a higher rate so the payment does not only work under today’s assumption.
- Check affordability against household income and committed outgoings, not just the lender’s headline loan size.
- Add SDLT, legal fees, survey costs, and moving expenses to the cash needed before making an offer.
Go deeper — 4 guides reference this calculator
First-Time Buyer Mortgage Guide: Schemes, LTVs, Stamp Duty Relief
Everything a UK first-time buyer needs to know about mortgages — typical LTVs, Help-to-Buy, Lifetime ISA, stamp duty relief thresholds, and realistic budgets.
UK Mortgage Overpayments Guide: When to Clear Faster and When to Save Cash
How mortgage overpayments work, when they save the most interest, when early repayment charges matter, and when your cash should stay liquid instead.
UK Stamp Duty (SDLT) Explained: Rates from 1 April 2025, First-Time Buyer Relief, Second-Home Surcharge
Clear walkthrough of UK Stamp Duty Land Tax — current bands, first-home relief up to £500,000 (0% to £300,000), +5% additional-property surcharge, and worked examples.
Buy-to-Let Mortgage Guide: ICR, Rates, Section 24 & Limited Company
UK buy-to-let landlord guide — BTL mortgage rates and LTVs, Interest Coverage Ratio, Section 24 impact, limited-company vs personal ownership, and real net yields.
Frequently asked
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