Mortgage Offset vs Extra Repayment Calculator
Compare keeping spare cash in an offset account with paying it directly into your mortgage. See how interest and fees change while keeping access to the money visible.
Calculation breakdown
How to use this tool
- Enter your loan and payment details.
- Use the same spare-cash amount in both scenarios.
- Add offset fees and any redraw events, then compare the schedules.
How the result is calculated
A full offset reduces the balance used to calculate interest. An extra repayment reduces the loan principal. Those can produce similar interest effects but different account balances and access conditions.
Worked example
A $300,000 mortgage with $20,000 in a full offset calculates interest on $280,000. At an illustrative steady 6%, that offset saves about $1,200 a year before fees.
What this result does not cover
Lender terms, daily balances and rate changes affect results. The calculator does not determine tax deductibility or guarantee redraw access.
Questions people ask
Is redraw the same as an offset account?
No. The money and access rules are structured differently.
Can fees cancel the interest saving?
Yes. Compare net saving after package and account fees.
Can an offset generate negative interest?
No. The model floors the interest-bearing balance at zero.
Supported scope and official sources
Daily simple interest accumulated and posted at month end. Opening cash and each event are identical in both scenarios. Beginning-of-day cash events, then regular payment, then daily interest; interest posts at month end. Fees are external cash costs. Redraw limited to modeled extra contributions; lender access is never guaranteed. Up to 10 years.
Source snapshot: 22 October 2026. Independent specialist review is pending. Calculations do not confirm eligibility or replace official decisions.