Rate change calculator
Put your current rate against a different one and see what it does to the monthly payment. Useful for stress-testing a rise before it arrives, and for sizing the gap between a new deal and the standard variable rate you would otherwise roll onto.
The two questions this answers
Answer first: what would a rise cost me? and what is staying put costing me? They are the same calculation pointed in opposite directions, and both are worth running.
The first is a stress test. If you are considering a tracker, or your fix ends soon, modelling a rate a point or two above today's tells you whether the payment would still be comfortable. Better to discover that now than when it happens.
Sizing the SVR gap
The second use is more urgent for anyone whose deal has ended. Put your current rate in as the new rate and the deal rate you could get as the old one, and the difference is what drifting is costing you every month.
For most people that gap is the largest single saving available in the mortgage market — considerably larger than the difference between the best lender and the second best. What the SVR really costs sets out the scale, and there is normally no penalty for leaving an SVR, so nothing is holding you there.
What actually moves your rate
If you are on a tracker, the Bank of England base rate moves your payment directly. If you are on a fixed rate, nothing moves until the deal ends — but the rates available to you when it does are driven by swap rates, which can shift even when the base rate does not.
That last point catches people out: a base rate hold does not mean the deals on offer have stayed still. Swap rates explained covers why, and the base rate and your mortgage covers what changes for each product type.
Rate change, answered
How much does a 1% rate rise cost per month?+
It depends on the balance and the remaining term — the larger the balance, the bigger the effect. Entering your own figures gives the real answer, which is usually more significant than people expect on a typical mortgage balance.
What happens when my fixed rate ends?+
Unless you act, you roll onto the lender's standard variable rate, which is typically far more expensive than any new deal. Putting your deal rate against the SVR in this calculator shows the monthly cost of doing nothing.
Should I fix if rates might rise?+
Fixing buys certainty at a price; a tracker keeps flexibility and passes on any falls. Neither is automatically right, and it depends on how much payment variation you can absorb and how long you will hold the mortgage. Model a rise here and see whether the higher payment would still work for you.
Why did my fixed-rate options change when the base rate didn't?+
Because fixed rates are priced off swap rates, which reflect what markets expect rates to do in future rather than where they are today. Fixed pricing can move substantially in a week when the Bank of England has done nothing at all.