FinToolSuite

Mortgage Overpayment Savings Calculator

Updated April 17, 2026 · Mortgage · Educational use only ·

Interest saved and years shaved by overpaying.

Calculate interest saved and years shaved off your mortgage by making regular monthly overpayments. Enter loan amount and rate for an instant result.

What this tool does

Enter loan, rate, term, and overpayment amount. The tool shows interest saved and time off the term.

Enter Values
Formula Used
Without overpayment
With overpayment

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Disclaimer

Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.

200,000 at 5% over 25 years with 200/month overpayment pays off 6.5 years early and saves around 41,800 in interest. Even modest overpayments compound dramatically over long terms. Most mortgages allow 10% of balance per year fee-free; check yours before starting.

A worked example

Try the defaults: loan amount of 200,000, annual rate of 5%, original term of 25, monthly overpayment of 200. The tool returns 41,842.60. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.

What moves the number most

The result responds to Loan Amount, Annual Rate, Original Term, and Monthly Overpayment. Not every input has equal weight. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.

The formula behind this

Simulate monthly amortisation with overpayment until balance clears. Compare total interest paid to standard amortisation. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.

What the headline rate hides

Lenders quote a rate; what you pay is a blend of that rate, fees, insurance, and any early-repayment penalty built into the product. The figure here isolates the core interest cost so you can compare like-for-like across deals — then add the other costs separately before signing anything.

What this doesn't capture

The figure excludes arrangement fees, valuation costs, legal fees, insurance, and any early-repayment charges — those can add several thousand to the headline cost. Rate changes at renewal for fixed-term deals will shift the picture further. Use this for the core interest/principal math and add the other costs on top.

Example Scenario

Overpayment savings produces an interest saving based on the inputs provided.

Inputs

Loan Amount:200,000 £
Annual Rate:5
Original Term:25 years
Monthly Overpayment:200 £
Expected Result£41,842.60

This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.

Sources & Methodology

Methodology

Simulate monthly amortisation with overpayment until balance clears. Compare total interest paid to standard amortisation.

Frequently Asked Questions

Does my mortgage allow overpayments?
Most do, with limits. Fixed-rate typically allow 10% of balance per year without penalty; above that triggers early-repayment charges.
Better to overpay or invest?
Overpay if mortgage rate exceeds expected investment return. Invest if return is higher. Equal return slightly favours investing due to flexibility.
Should I overpay or reduce term?
Overpayment is flexible (can stop); term reduction is committed. Both save similar interest if contribution is equal. Overpayment wins for most unless you want to force discipline.
One-off overpayment?
Even better per pound than monthly. A 10k lump sum early in a 25-year term saves more than 10k spread monthly over those 25 years.

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