Work out your monthly repayment or interest-only mortgage payment, plus a full Stamp Duty Land Tax (SDLT) breakdown with First-Time Buyer relief — England & Northern Ireland rates, in £.
| # | Payment | Principal | Interest | Balance |
|---|
Enter Property & Mortgage Details
Fill in the property price, deposit, term, and interest rate, then click Calculate to see your monthly payment and full SDLT breakdown.
A UK mortgage calculator needs to answer two questions that don't come up in most other countries' mortgage math: whether you're paying down the loan or just servicing interest, and how much Stamp Duty Land Tax (SDLT) you'll owe HMRC on completion day. NeftCal's UK Mortgage Calculator handles both. Toggle between a standard repayment mortgage — where every monthly payment chips away at the capital until the loan hits zero — and an interest-only mortgage, where the payment covers interest alone and the full loan balance falls due as a lump sum at the end of the term. Alongside the payment, it works out your SDLT bill using the current progressive England & Northern Ireland bands, including First-Time Buyer relief where it applies.
UK mortgages are typically quoted with a deposit (often 5–10% minimum, though 15–25%+ unlocks better rates), a term of 20–35 years, and an annual interest rate. This calculator takes those inputs, works out your loan amount, and applies the standard amortization formula for repayment mode or a simple flat-interest calculation for interest-only mode. On top of the payment, it separately computes SDLT — a one-off tax due on most property purchases in England and Northern Ireland, charged in bands so that only the portion of the price within each band is taxed at that band's rate, not the whole purchase price at once.
First-time buyers sizing up a purchase before making an offer, home movers comparing repayment vs. interest-only against their existing mortgage, landlords and investors modeling a buy-to-let purchase's cash flow, and anyone remortgaging who wants to compare a new rate and term against their current deal will all find this useful. It's equally suited to a quick affordability gut-check and to a detailed side-by-side comparison of terms and rates.
A mortgage is usually the largest recurring cost in a UK household budget, and SDLT is often the largest one-off cash requirement on top of the deposit — both need to be budgeted for well before completion. Understanding whether interest-only's lower monthly payment is worth the risk of an un-repaid lump sum at the end, and exactly how much SDLT a given price point triggers, are two of the most consequential decisions in a UK property purchase.
The mortgage payment and Stamp Duty Land Tax are two separate calculations, both shown in full below
From property price to full payment and SDLT breakdown in under a minute
Pick Repayment mode for a standard capital-and-interest mortgage, or Interest-Only mode to see a flat interest-only payment with the loan due in full at the end of the term.
Input the property price, then enter your deposit as a percentage or a £ amount — both fields stay in sync automatically.
Choose a term between 20 and 35 years and enter your quoted annual interest rate, or use the typical-range hint as a starting point.
If you're a first-time buyer, tick the box to apply SDLT relief automatically on properties priced at £625,000 or less.
Click Calculate to see your monthly payment, loan amount, total interest, and full Stamp Duty Land Tax breakdown, along with charts and a 12-month payment schedule.
A realistic UK purchase using this calculator's default settings
Suppose you're buying a £350,000 property with a 10% deposit (£35,000), leaving a £315,000 loan, over a 25-year (300-month) term at a 5.5% annual interest rate, in Repayment mode, and you are not a first-time buyer.
| Payment # | Payment | Interest | Principal | Remaining Balance |
|---|---|---|---|---|
| 1 | £1,934.38 | £1,443.75 | £490.63 | £314,509.37 |
| 2 | £1,934.38 | £1,441.50 | £492.87 | £314,016.50 |
| 3 | £1,934.38 | £1,439.24 | £495.13 | £313,521.37 |
Explanation: On this £315,000 loan, the first month's interest of £1,443.75 makes up nearly 75% of the payment, with only £490.63 going toward the balance — typical of the early years of a long repayment term, where the principal share grows slowly at first and then accelerates. Over the full 25 years, the loan costs £265,312.68 in interest, roughly 84% of the amount borrowed.
Interest-only comparison: Switching the same £315,000 loan to Interest-Only mode at 5.5% gives a flat monthly payment of £315,000 × 0.0045833 = £1,443.75/month — about £490.63 less than the repayment figure above. But because none of the capital is ever repaid, the total interest paid over 25 years is £1,443.75 × 300 = £433,125, and the full £315,000 is still owed as a lump sum when the term ends — £167,812 more in interest than repayment mode, plus the un-repaid capital still outstanding.
Is your loan-to-value ratio, and your SDLT bill, in a comfortable range?
Lenders talk about loan-to-value (LTV) — your loan amount as a percentage of the property price — because it drives both your interest rate and your risk. A lower LTV (bigger deposit) almost always means a better rate.
| Loan-to-Value (LTV) | General Read | Typical Context |
|---|---|---|
| Under 75% | Strong position | Typically unlocks the most competitive interest rates |
| 75% – 90% | Common, moderate rates | Where most first-time buyers and home movers land |
| Over 90% | Higher rates, less choice | Fewer lenders and products; higher interest rate typically applies |
For buyers: if your deposit puts you above 90% LTV, consider whether a slightly larger deposit — even a few percentage points — moves you into a materially cheaper rate band before you commit to a lender.
SDLT as a completion-day cost: unlike your deposit, SDLT is due in full alongside the property purchase and is not something you can mortgage — budget for it in cash, separately from your deposit and moving costs.
Risk considerations: this calculator assumes a fixed rate for the full term. It doesn't capture what happens when a fixed or tracker deal ends and you move to your lender's standard variable rate (SVR), which is usually higher — always plan to review your mortgage before any initial deal period expires.
This tool provides general financial estimates for educational purposes only and does not constitute personalized financial, tax, or legal advice. SDLT rates and bands are set by HMRC and the UK government and change periodically, and this calculator's SDLT figures apply to England & Northern Ireland only — Scotland (LBTT) and Wales (LTT) use different taxes with different bands and thresholds. Confirm final SDLT and mortgage figures with a solicitor, conveyancer, or mortgage broker before proceeding with a purchase.
Where this calculator earns its keep
Check your monthly payment and SDLT relief eligibility before making an offer on your first home.
Compare your new mortgage's payment and term against your existing deal before moving house.
Model an interest-only payment against expected rental income for a landlord purchase.
Work out your exact completion-day Stamp Duty bill before agreeing a purchase price.
Compare 20-, 25-, 30-, and 35-year terms side by side to see the payment-vs-total-interest trade-off.
See how increasing your deposit lowers your loan-to-value, monthly payment, and total interest.
Directly compare the monthly saving of interest-only against the un-repaid lump sum at the end.
See exactly how much extra SDLT a purchase price just above £250,000, £425,000, or £625,000 triggers.
Re-run the calculation at different quoted rates to see how a 0.25–0.5% difference changes your monthly payment.
Neither approach is universally "better" — it depends on your plan for the capital
Standard rates vs. First-Time Buyer relief bands, side by side
| Price Band | Standard Rate | First-Time Buyer Rate |
|---|---|---|
| £0 – £250,000 | 0% | 0% (up to £425,000) |
| £250,001 – £425,000 | 5% | |
| £425,001 – £625,000 | 5% | 5% (£425,001–£625,000) |
| £625,001 – £925,000 | 5% | No relief — standard rates apply in full |
| £925,001 – £1,500,000 | 10% | No relief — standard rates apply in full |
| Above £1,500,000 | 12% | No relief — standard rates apply in full |
How to read this table: each row's rate applies only to the slice of the price that falls within that band — not the whole purchase price. First-Time Buyer relief only exists at all when the total price is £625,000 or less; above that threshold, buyers pay the standard rates with no relief, exactly as if they were not first-time buyers.
Common questions about UK mortgage payments and Stamp Duty Land Tax
Official guidance to complement this calculator — not a substitute for licensed financial or legal advice
Explore other financial tools