How to Use the Mortgage Calculator
Our free mortgage calculator works out your monthly repayment based on four inputs:
- Property Price — the full purchase price of the home
- Deposit — the amount you're putting down upfront (minimum 5%)
- Interest Rate — use the current best rate (3.94%) or your lender's offered rate
- Mortgage Term — how many years to repay (typically 25–35 years)
The calculator shows your monthly payment, total amount repaid, total interest paid, LTV ratio and an estimate of stamp duty.
Expert Tip
A longer mortgage term (e.g. 35 years instead of 25) lowers your monthly payment but significantly increases total interest paid. On a £250,000 mortgage at 4%: 25yr = £1,319/mo (£145,700 interest) vs 35yr = £1,098/mo (£211,300 interest). The MoneyHelper mortgage calculator ↗ is a government-backed alternative.
LTV — Loan to Value Explained
LTV (Loan to Value) is your mortgage loan as a percentage of the property's value. It determines which mortgage rates you can access:
| LTV | Deposit Needed | Rate Access | Example (£300k property) |
|---|---|---|---|
| 60% LTV | 40% (£120,000) | Best rates available | Loan: £180,000 |
| 75% LTV | 25% (£75,000) | Excellent rates | Loan: £225,000 |
| 80% LTV | 20% (£60,000) | Good rates | Loan: £240,000 |
| 85% LTV | 15% (£45,000) | Standard rates | Loan: £255,000 |
| 90% LTV | 10% (£30,000) | Higher rates | Loan: £270,000 |
| 95% LTV | 5% (£15,000) | Highest rates | Loan: £285,000 |
Stamp Duty 2025/26 (England)
Stamp Duty Land Tax (SDLT) is a tax on property purchases in England. The current thresholds for 2025/26 are:
- Up to £250,000: 0%
- £250,001 – £925,000: 5%
- £925,001 – £1.5m: 10%
- Over £1.5m: 12%
First-time buyers pay no stamp duty on the first £425,000 (up to a property price of £625,000). For the official calculator, see HMRC Stamp Duty Calculator ↗.
- Get a soft-search decision in principle before house-hunting — it costs nothing and reveals problems early
- Start remortgage shopping 6 months before your fix ends — you can lock now and switch if rates fall
- Compare total cost over the fixed period — rate plus fees, not headline rate alone
- Whole-of-market brokers see deals comparison sites never list, especially for non-standard income
What the Comparison Sites Won't Tell You
Buying new-build changes the process: developer deadlines (often 28 days to exchange), incentives that lenders may deduct from the valuation, and the need for extended offer validity. Tell your broker it's new-build on day one.
Timing your remortgage matters more than most borrowers realise. Most lenders let you lock a deal half a year ahead — if rates rise you're protected, and if they fall you can usually re-lock lower before completion.
Get your decision in principle before falling in love with a property. It's a soft-search estimate of your borrowing power that strengthens any offer you make, and it surfaces problems months before they can derail a purchase.
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