Advanced Mortgage Overpayment Calculator

See the impact of monthly payments and one-off lump sums.

Base Mortgage Details

£
%
1 yr 25 yrs 40 yrs

Overpayment Strategy

£
£

e.g. Month 12 is 1 year from now.

Standard Payoff 25.0 yrs
New Payoff Term 18.5 yrs
Total Interest Saved £0
Time Saved 0 yrs

Savings Breakdown

Calculating...

The Power of One-Off Mortgage Overpayments

While regular monthly overpayments are a fantastic way to chip away at debt, one-off lump sum overpayments can be even more effective due to the way interest compounds. By making a significant payment early in your mortgage term, you immediately reduce the principal balance upon which all future interest is calculated.

Monthly vs. One-Off Payments

Using this calculator, you can compare a steady monthly overpayment strategy against a single lump sum payment (such as an annual bonus or tax refund). Often, making a one-off payment of £5,000 in Year 1 of a mortgage can save significantly more in total interest than the same £5,000 spread out over several years.

Strategic Timing

The "Occurs in Month" feature allows you to see how timing affects your savings. Generally, the earlier the overpayment occurs, the greater the interest saving. This is because you are stopping that portion of the debt from accruing interest for the remainder of the 25 or 30-year term.