Offset Mortgage Calculator
Updated on 22 Oct 2026 · Checked by Aotob
Keeping $30,000 in an offset account saves $73,917 of interest.
The mortgage is paid off 3 years 4 months early with the same payment.
Interest saved
$73,917
Savings in an offset account “earn” the mortgage rate, 5.5%, tax-free, and you can still take them out. That beats most savings accounts once tax is counted.
Show the working
Interest each month on (balance − 30,000) × 5.5% ÷ 12
252,679 − 178,762 = 73,917
By savings kept
| Savings | Interest saved | Years sooner |
|---|---|---|
| 7,500 | 21,097 | 0.9 |
| 15,000 | 40,300 | 1.8 |
| 30,000 | 73,917 | 3.3 |
| 60,000 | 126,452 | 5.7 |
| 90,000 | 164,918 | 7.4 |
Questions people ask
How does an offset mortgage work?
Savings in a linked account are taken off the mortgage balance before interest is charged. You earn no interest on them, but you pay less on the mortgage.
Is it better than a savings account?
Often, because the saving is tax-free and the mortgage rate is usually higher than savings rates after tax.
Offset or overpay?
Overpaying saves the same interest but locks the money in. Offset keeps it available, usually at a slightly higher mortgage rate.
Updated 22 Oct 2026Source: Standard loan maths, checked October 2026Checked by AotobSavings kept the same all the time; same rate for the whole term.Report an issue