Interest-only change / month
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Enter your balance, term and two rates — current and prospective — to see the payment difference in pounds. The calculator answers the questions rate news always raises: what does the base rate move mean for me, what happens when my fix expires onto today's pricing, what would the remortgage offer actually save?
The personal arithmetic matters because headlines never carry it: a quarter-point move is trivial on a small balance near term-end and substantial on a large recent loan, and only your own numbers say which you are.
Fix expiry is the big one: your deal rate against the current market (or your lender's standard variable rate, the default you drift onto by doing nothing) shows the cost of inaction and the value of the remortgage we would start six months out. Base rate moves matter directly on trackers and variables, and indirectly on the fixed pricing you will face at expiry.
Affordability stress is the forward-looking run: your payment at 2-3% above today's rate is the resilience test lenders apply and households should too — particularly contractors, whose income-side buffers and rate-side exposure deserve planning together.
The calculator quantifies; the response is strategic: expiring fixes trigger the remortgage comparison (with the contractor reassessment opportunity our remortgage page maps), rate anxiety on variables raises the fix-now question, and stressed payments that look uncomfortable raise term, structure and overpayment levers in combination.
We run the live versions of all of these — your actual deals, today's actual pricing — as the standing service behind the calculator's approximations.
On trackers and variables, roughly £12-13 per month per £100,000 of balance at typical terms — your exact figure depends on balance and remaining term, which is what the calculator personalises. Fixed rates feel base moves only at expiry, through the pricing you remortgage into.
You drift onto the standard variable rate — typically far above market pricing, and the most expensive default in the mortgage. The calculator shows the drift’s monthly cost; the remortgage process we start six months out is the prevention.
Nobody knows rates’ path — including us, honestly. What the calculator can do is quantify each scenario on your numbers, and what we can add is the structure decisions (fix length, tracker-with-switch options, ERC flexibility) that manage the uncertainty rather than betting on it.
2-3% above today’s rate mirrors lender affordability stresses — a payment comfortable there is resilient. For contractors, the rate stress pairs with the income stress (the gap-and-buffer planning this site maps) as the two halves of household resilience.