Tracker Mortgage Calculator

Your mortgage

Amount borrowed (£) Bank of England base rate (%) Current rate, held at the June 2026 MPC meeting Tracker margin above base (%) Term (years)

Overpayment mode

Total spend per mortgage year (£) Measured 1 Aug – 31 Jul: six monthly payments, then the 1 Feb lump sum, then six more at the new lower payment. The lump is solved so the total lands exactly on this figure.

Mortgage starts1 Aug 2026

First payment1 Sep 2026

Scheduled final payment–

Starting pay rate–

How it works: interest is charged monthly on the outstanding balance at base + margin. Each 1 February a one-off overpayment comes straight off the balance, then the monthly payment is recalculated over the remaining term — so the term stays fixed and the monthly payment falls instead. In target mode the lump sum is solved so the mortgage year's total cash out hits your figure exactly. That takes a little algebra rather than a guess, because the lump changes the new monthly payment, which in turn changes how much room is left for the lump.

Starting monthly payment

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Final monthly payment

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Total interest

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Total overpaid

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Mortgage cleared

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Year-by-year projection & overpayment planner

Date	Balance before	Overpayment	New base rate	Pay rate	Balance after	New monthly payment	Change	Total spend, mortgage yr ‡	Interest, 12m to date †

† “Interest, 12m to date” looks backwards, not forwards. It is the interest charged over the twelve months ending on that row's date — so the row dated 1 Feb 2028 covers Feb 2027 to Jan 2028. Every other figure on the row (the overpayment, the rate, the new monthly payment) applies to the year ahead, so this one column runs the opposite way. Two consequences: the first row is a six-month stub covering only Aug 2026 to Jan 2027, so it is not comparable with the rows below it; and the final Feb–Jul stub is not shown on any row, so this column sums to slightly less than the total interest on the summary card. The card is the correct total.

‡ “Total spend, mortgage yr” is the actual cash leaving your account over the mortgage year 1 Aug – 31 Jul that straddles this row: six monthly payments at the old rate, then the lump sum, then six at the new rate. In target mode this is the column driven to your target figure, so it should read exactly your target on every full year.

Detail

Payment date	Payment	Interest	Capital	Overpayment	Rate	Balance