About this calculator
The Bank of England moves Bank Rate in steps — usually a quarter of a percentage point — and headlines report the step, never what it does to a household budget. The translation is not linear in the way people expect: a 0.25-point rise on £200,000 over 25 years adds about £29 a month; a full point adds about £117. The same rise on a £400,000 balance doubles those figures, while on a £75,000 balance near the end of its term it is loose change. Balance and remaining term are everything, which is why this calculator works on yours, not on an "average mortgage".
Two groups feel a rate move directly: tracker borrowers, whose rate follows Bank Rate mechanically, and SVR borrowers, whose lender usually passes most of a move on. Everyone on a fix is insulated until the deal ends — for them this calculator answers a different question: what will my payment jump to if rates are still here when I come to re-fix? Run it at your deal's end date scenario, and compare with the remortgage calculator before the renewal letter arrives.
How to use it
- Enter your balance, current rate and the years left — from your latest statement.
- Enter the rate change in percentage points: +0.25 for a typical Bank Rate rise, −0.50 for two cuts, +1 or +2 to stress-test yourself.
- Read the change in the monthly payment and in total interest across the whole remaining term.
- Scan the scenario table for the full ladder; every row is worked out on your balance and term.
The formula
The payment formula is non-linear in the rate: the same 0.25-point step costs slightly more at higher starting rates and much more on larger balances and longer terms, because more of each early payment is interest. The scenario table fixes the balance and term and varies only the rate, isolating that effect.
Worked example
£200,000 at 4.50% with 25 years left costs £1,111.66 a month and £133,499 of interest in total. A half-point rise to 5.00% lifts the payment to £1,169.18 — £57.52 more a month — and the lifetime interest by £17,255 to £150,754. A half-point fall to 4.00% takes the payment to £1,055.67 — £55.99 a month saved, and £16,797 less interest over the term. Now scale it: on a £350,000 balance the same half point is about £101 a month — which is why rate news that sounds identical lands so differently on different households.
Sources: Standard amortization mathematics; scenario steps use the quarter-point increments in which the Bank of England typically moves Bank Rate. Last updated: October 2026.
Frequently asked questions
How much does a 0.25% rate rise add to a £200,000 mortgage?
About £29 a month at typical rates and terms (£200,000, 25 years left, starting near 4.50%: £1,111.66 rising to about £1,140). Over the full remaining term that single quarter point is roughly £8,600 of extra interest if the rate stayed there. Use the calculator with your exact balance and term — the figure scales almost proportionally with the balance.
Bank Rate moved — why has my payment not changed?
If you are on a fixed rate, it will not change until your deal ends; the rise matters at renewal time. Trackers move with Bank Rate (usually within a month), and SVR borrowers are at their lender's discretion — most SVRs follow Bank Rate up quickly and down slowly. Check which product you are actually on before worrying.
Should I fix now or wait for rates to fall?
Nobody knows the path of rates — including the Bank of England. The useful comparison is personal: fix for certainty of payment over the period you need it, and run this calculator at +1% and +2% on your balance. If a +2% world would break your budget at renewal, fixing longer buys real insurance; if you could absorb it easily, a shorter fix keeps your options open.
Does a rate change affect how fast I pay off the capital?
Yes, quietly: with a fixed payment amount, a lower rate means more of each payment is capital, so the balance falls faster than scheduled (and vice versa). Lenders normally recalculate your payment when the rate changes so the original end date stands — this calculator follows that convention.
What formula does this uk mortgage rate change calculator use?
New rate = current rate + change. Both payments use M = P × r(1 + r)^n ÷ ((1 + r)^n − 1) with the new monthly rate r; the monthly difference is M(new) − M(current), and the interest figures come from simulating every remaining month at each rate. The payment formula is non-linear in the rate: the same 0.25-point step costs slightly more at higher starting rates and much more on larger balances and longer terms, because more of each early payment is interest. The scenario table fixes the balance and term and varies only the rate, isolating that effect. The worked example on this page applies the formula step by step with real numbers, so you can verify the result by hand.