The method
How it is worked out
Saving = interest at current payment − interest at (payment + extra) − early-repayment charge
- extra
- Additional amount paid each month
Loan Overpayment Calculator
See how much interest an extra monthly payment saves and how many months it cuts, versus investing the same money. The result updates as you type so you can compare scenarios quickly.
Keep in mind
What it leaves out
- Overpayment limitsMany loans and mortgages cap penalty-free overpayments (often 10% a year).
- Emergency fundKeep cash reserves before overpaying.
- TaxInvestment returns may be taxed; loan interest saved is not.
Use the calculator to compare scenarios rather than as a guaranteed forecast.
About the Loan Overpayment Calculator
See how much interest an extra monthly payment saves and how many months it cuts from a loan or mortgage, then compare that certain saving with investing the same money.
How it works and an example to tryShow less
How to use the result
The loan is run month by month at the current payment and again with the extra payment, comparing total interest and months to clear. The extra payments are also compounded at your expected investment return over the shorter loan term for comparison.
Example to try
Paying £150 extra on an £18,000 balance at 7.5% with a £400 payment saves about £1,000 of interest and clears the loan 15 months sooner. Investing £150 a month at 5% over the same time would earn roughly £700.
Put it to work
Try it on a real situation
Load an example
What moves the result most
Worked out from your figures above. Tap a row to try it.
Who uses it, and when
Borrowers with spare monthly cash, mortgage holders comparing overpaying with pension or ISA contributions, and anyone weighing a guaranteed saving against an uncertain return.
Mistakes worth avoiding
- Overpaying while carrying dearer debt elsewhere.
- Overpaying beyond the penalty-free limit and triggering a charge.
- Emptying your emergency fund to overpay.
Questions
What does the Loan Overpayment Calculator do?
See how much interest an extra monthly payment saves and how many months it cuts, versus investing the same money.
How should I use the result?
The loan is run month by month at the current payment and again with the extra payment, comparing total interest and months to clear. The extra payments are also compounded at your expected investment return over the shorter loan term for comparison.
Does TechBullion store the information I enter?
The core calculation or transformation runs in your browser. Normal website security and analytics may still record page-level events, but the tool does not need to create a public record from your inputs.
What mistakes do people make with a loan overpayment calculator?
Overpaying while carrying dearer debt elsewhere. Overpaying beyond the penalty-free limit and triggering a charge. Emptying your emergency fund to overpay.
Is the result guaranteed?
No. Use the result as a practical check or planning aid and verify important decisions with the relevant primary source, provider or professional advice.
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Results are estimates based on the figures entered, for general information only, and not financial, investment, tax or legal advice. See our terms of use.