About the Mortgage Calculator UK
A UK mortgage calculator estimates the monthly repayment on a property purchase and adds an estimate of Stamp Duty Land Tax, which is often the largest single cost buyers forget to budget for. Both are needed to know what a purchase really requires up front and each month.
The formula
M = P · [ r(1 + r)ⁿ ] / [ (1 + r)ⁿ − 1 ]P is the property price less your deposit, r is the monthly rate, and n is the number of monthly payments. Stamp duty is charged in bands on the purchase price, so only the portion within each band is taxed at that band's rate.
How to use this calculator
- 1Enter your Property Price (£). The field starts at
300000, which you can overwrite. - 2Enter your Deposit (£). The field starts at
60000, which you can overwrite. - 3Enter your Interest Rate (%). The field starts at
5.5, which you can overwrite. - 4Enter your Mortgage Term (Years). The field starts at
25, which you can overwrite. - 5Read the result straight away — it recalculates as you type, so there is no button to press. Use Share to copy a link that reopens the page with your exact numbers filled in.
Worked example
| Input | Value |
|---|---|
| Property Price (£) | 300000 |
| Deposit (£) | 60000 |
| Interest Rate (%) | 5.5 |
| Mortgage Term (Years) | 25 |
Result
Monthly Payment: £1473.81
Total Interest: £202,142.994
LTV Ratio: 80.0%
Est. Stamp Duty: £2,500.00
Those are the values the page loads with, so you can reproduce this result yourself and then change one field at a time to see what drives the outcome.
Understanding your result
UK mortgages differ from US ones in an important way: the rate is normally fixed for an initial period of two to five years, not the full term, after which you revert to the lender's standard variable rate. The payment shown here reflects your entered rate, so treat it as the cost during the fixed period rather than for the whole 25 years.
Stamp duty is tiered rather than flat. Each band applies only to the slice of the price falling within it, so the effective rate is always lower than the top band you touch. Rates differ for first-time buyers, additional properties, and non-UK residents, and Scotland and Wales operate separate taxes entirely.
Things worth knowing
- Plan for the reversion. When the fixed period ends, the standard variable rate is usually considerably higher, so budget for a remortgage.
- Loan-to-value drives pricing in tiers. Getting to 90, 85, or 75 percent can move you into a materially better rate band.
- First-time buyer stamp duty relief can save thousands, but it is withdrawn above a price threshold.
- Add solicitor fees, survey, and valuation costs to your upfront budget alongside the deposit and stamp duty.
- Scotland charges Land and Buildings Transaction Tax and Wales charges Land Transaction Tax, with different bands from England.
Frequently asked questions
How much deposit do I need for a UK mortgage?+
Five percent is the practical minimum for most lenders, but rates improve markedly at 10, 15, and 25 percent. A larger deposit lowers your loan-to-value and moves you into cheaper pricing tiers.
How is stamp duty calculated?+
In bands, with each rate applying only to the portion of the price within that band. First-time buyers receive relief up to a threshold, and additional properties attract a surcharge on every band.
What happens when my fixed rate ends?+
You move automatically onto the lender's standard variable rate, which is typically much higher. Most borrowers remortgage onto a new fixed deal a few months before the current one expires.
Should I choose repayment or interest-only?+
Repayment clears the debt by the end of the term and is standard for residential purchases. Interest-only keeps payments lower but leaves the full balance outstanding, so lenders require a credible repayment plan and mostly restrict it to buy-to-let.