Overpayment Calculator
See how a small extra each month — or a one-off lump sum — shortens your term and slashes the interest you'll pay.
How the numbers land.
Three steps from input to a figure you can plan around.
Enter your mortgage
Current balance, rate, remaining term, and a regular overpayment or lump sum.
See the saving
New payoff date, total interest saved, and how the saving splits between time and money.
Check your ERC
Most fixed-rate deals cap penalty-free overpayments at 10% per year. Confirm yours before committing.
Talk to an adviser
Key figures behind this calculator
10%
Typical annual ERC-free cap
£100/mo
Saves thousands over 25 years
0%
Cap on tracker / SVR
What we assume.
Every calculator is a model. Here's where ours rounds, simplifies, or hands the detail to a real adviser.
Standard 10% allowance
Calculator assumes overpayments stay within most lenders' annual penalty-free limit. Above that, fixed-rate deals charge ERCs we don't deduct.
Term shortens, payment held
We model the saving as a shorter term with the same monthly payment — usually the cheapest outcome. Some lenders default to lower payments instead.
No rate change modelled
Your rate stays flat for the projection. After your fix expires, the actual saving depends on your remortgage rate.
No tax / investment trade-off
For higher earners, ISA or pension contributions may beat overpaying. The calculator doesn't compare them.
Frequently asked.
Most UK fixed-rate mortgages allow 10% of the outstanding balance per year as a penalty-free overpayment. Trackers, variables and outside-fix periods often have no cap. Always check your specific deal.
Still got a question we haven't answered?
Talk to an adviserMore to figure out.
Browse all calculatorsFrom figure to offer.
Calculators give you a useful estimate. The real number depends on your full circumstances, credit profile, and the lender that ultimately approves the case. Our CeMAP-qualified advisers compare 90+ UK lenders and translate the overpayment calculator into a deal you can actually take.
No-obligation chat
Book a call — we'll discuss your situation and what you're trying to achieve, no commitment.
Higher approval confidence
Our brokers know which lenders suit first-time buyers, remortgagers, buy-to-let, and complex cases.
Service that performs
Clear communication, realistic timelines, and the right product — not just the lowest headline rate.