Mortgage Overpayment Calculator
Even small monthly overpayments save thousands in interest over the term.
Updated May 2026, using HMRC 2026/27 rates and current ONS / gov.uk figures.
Most UK mortgage products allow 10% per year overpayment penalty-free during the fixed period. Overpayment reduces the capital, so future interest is calculated on a smaller balance.
Worked examples
£200k mortgage at 5% over 25 years: £1,170/mo. Overpaying £100/mo saves ~£30k interest, takes ~3 years off the term.
10% overpayment in year 1 on £200k = £20k off the capital. Saves ~£35k over 25 years.
Frequently asked questions
Are there penalties?
During the fixed period, most lenders cap free overpayments at 10%/yr. Beyond that, an early-repayment charge (1-5%) typically applies. After the fixed period, you can usually overpay without limit.
Lump sum or monthly?
Lump sums save more interest the earlier in the term. Monthly is easier to budget but slightly less efficient.