Mortgage Calculator

Mid-term overpayment calculator — see the effect of monthly overpayments and interest-rate changes over the rest of your mortgage. Have your remaining balance to hand.

If you are on a fixed rate, enter that term and rate. Use the market rate (default 6%) for payments after the fix ends. With no fixed term, the market rate is used throughout.

Disclaimer: This calculator is a guide only. Please run your own calculations before making any decisions.

Your Mortgage

House Value On Renewal (optional)

Leave blank to assume the same as purchase house price. Used for LTV at renewal.

Remaining Mortgage Lifetime
Remaining Fixed Term

Optional — leave blank / zero if you have no fixed term.

Market rate applies after your fixed term ends, or for the whole term if you have no fix.

Overpayments

Optional. Use start month if overpayments begin part-way through the remaining term.

One-off Payments

Extra lump sum on a specific month (e.g. month 14 = £2,000), on top of any monthly overpayment.

Reduce Lifetime: payments stay the same; you finish earlier.

Reduce Payments: monthly payments fall; term stays the same.

Check your mortgage agreement for which applies to you.

Results

Enter your mortgage details and hit Calculate to see interest totals, savings, and a full payment schedule.

Your mortgage data does not leave this page.

Built by Reece Daniels, with the help of ChatGPT & Cursor.

Disclaimer: Figures are best effort and may not reflect your own mortgage situation. Need a UK tax calculator?