Mortgages Overpayment Calculator
Mortgages overpayment calculator works out Payment and Total interest from Current loan balance, Annual interest rate and Loan term. The default figures on this page give interest saved by extra payments of 90,074.66; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
5 steps
- Scheduled payment on 200000 at 6.5% is 1264.14.
- Adding 200 of principal each period changes the payoff.
- Without extras: 360 payments and 255085.82 interest.
- With extras: 250 payments and 165011.16 interest.
- That saves 90074.66 and 110 payments (9.167 years).
Yearly summarytable
| year | interest | principal | endingBalance |
|---|---|---|---|
| 1 | 12,861.39 | 4,708.29 | 195,291.71 |
| 2 | 12,546.05 | 5,023.63 | 190,268.08 |
| 3 | 12,209.62 | 5,360.06 | 184,908.02 |
| 4 | 11,850.65 | 5,719.03 | 179,188.99 |
| 5 | 11,467.62 | 6,102.06 | 173,086.93 |
| 6 | 11,058.95 | 6,510.73 | 166,576.2 |
| 7 | 10,622.91 | 6,946.77 | 159,629.43 |
| 8 | 10,157.67 | 7,412.01 | 152,217.42 |
| 9 | 9,661.28 | 7,908.4 | 144,309.02 |
| 10 | 9,131.63 | 8,438.05 | 135,870.97 |
| 11 | 8,566.54 | 9,003.14 | 126,867.83 |
| 12 | 7,963.58 | 9,606.1 | 117,261.73 |
| 13 | 7,320.24 | 10,249.44 | 107,012.29 |
| 14 | 6,633.81 | 10,935.87 | 96,076.42 |
| 15 | 5,901.42 | 11,668.26 | 84,408.16 |
| 16 | 5,119.98 | 12,449.7 | 71,958.46 |
| 17 | 4,286.19 | 13,283.49 | 58,674.97 |
| 18 | 3,396.56 | 14,173.12 | 44,501.85 |
| 19 | 2,447.4 | 15,122.28 | 29,379.57 |
| 20 | 1,434.6 | 16,135.08 | 13,244.49 |
| 21 | 373.07 | 13,244.49 | 0 |
Its 6 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
2 sources
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What the mortgages overpayment calculator calculates
Compares a loan with and without extra principal payments, showing the interest saved and the time cut from the term.
How to use this mortgages overpayment calculator
Enter Current loan balance, Annual interest rate, Loan term and Term - additional months. Payment updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Payment, Total interest and Total of payments.
The method follows Standard annuity-immediate payment formula, PMT = P i / (1 - (1+i)^-n) and 12 CFR Part 1026 (Regulation Z), Appendix J - Annual Percentage Rate Computations.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
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Frequently asked questions
What is the mortgage overpayment trick?
On the figures this page opens with — current loan balance 300,000, annual interest rate 5%, loan term 30 years and extra principal each period 200 — the interest saved by extra payments is 90,074.66. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
What information do I need for the mortgages overpayment calculator?
You need Current loan balance, Annual interest rate, Loan term, Term - additional months, Payment frequency, Extra principal each period, One-off lump sum and Applied at payment number. The page opens with default figures that give interest saved by extra payments of 90,074.66, so you can see the scale before entering your own.
What does this mortgages overpayment calculator show?
It shows Payment, Total interest, Total of payments, Number of payments, Payoff time, Rate per period, Interest per unit borrowed and Interest saved by extra payments, with the working and any warnings for your entries.
Can I check how the mortgages overpayment calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.