Overview
This mortgage rate rise calculator shows how a change in interest rates could affect your monthly payment and the interest you pay. Enter your balance, current rate and remaining term, then a new rate to compare — you'll instantly see the new monthly payment, how much more (or less) that is, and the extra interest over your chosen horizon. A built-in stress-test table shows the impact at +0.5%, +1%, +2% and +3%, and you can add your income and essential costs to see how much monthly buffer you'd have left at each rate.
How it's calculated
When your rate changes, your lender normally recalculates the monthly payment so the balance still clears over the remaining term. We do the same:
- We recalculate the repayment at each rate over your remaining term.
- We total the interest across your chosen comparison horizon.
- We compare every scenario against your current payment.
If you're on a fixed rate, your payment won't change until the deal ends — so treat these as scenarios for when it does. On a tracker or variable rate, changes can feed through sooner.
New payment = repayment recalculated at the new rate over the remaining term
On an interest-only mortgage the payment is simply the interest each month (balance × rate ÷ 12), and the balance itself doesn't reduce.
Worked example
Take a £200,000 repayment mortgage with 25 years left, moving from 4.5% to 5.5% (a 1% rise):
| Payment at 4.5% | £1,112 | |
|---|---|---|
| Payment at 5.5% | £1,228 | |
| Monthly change | + £117 | about £1,400 a year |
| Extra interest over 5 years | ≈ £9,820 |
A 1% rise would add around £117 a month here — roughly £1,400 a year, and about £9,820 more interest over five years. The stress-test table shows +2% and +3% too, so you can see where the pressure points are before they arrive.
Current rates & key facts
Rate context & key facts
| Item | Detail |
|---|---|
| Bank of England base rate | 3.75% (June 2026) — trackers and SVRs move with it |
| Fixed-rate deals | Your payment is unchanged until the fixed period ends |
| Lender stress testing | Lenders check you could still afford repayments if rates rose |
Rates shown are illustrative scenarios, not forecasts. Your actual payment depends on your deal, lender and remaining term.
Last updated 18 June 2026 · Source: Bank of England — Bank Rate