Mortgage overpayment calculator — how to use it (Australia 2026)

Canonical tool: This article supports the pay off faster hub — the live mortgage payoff playground is the primary calculator. Model your loan there and email a PDF plan.

Most "overpayment calculators" online let you add one extra amount to one repayment schedule. Real Australian households stack fortnightly frequency, weekly extras, offset balances, EOFY lump sums, and sometimes a rate review — often in the same year.

This guide explains how to use the payoff hub without treating calculator output as a loan quote.

Step 1 — Enter your real loan basics

Start with:

• Current balance (not original loan size)
• Current rate (from your app — not the advertised new-customer rate)
• Remaining term (years left, not original 30)

If you are unsure of remaining term, check your lender statement or app amortisation view.

Step 2 — Set repayment frequency and lender method

Toggle fortnightly only after you confirm your lender uses the half-monthly method (half of monthly × 26). If they use true-period fortnightly, savings may be minimal — read the fortnightly trap guide before switching.

Step 3 — Layer extras and offset

Add extra repayments per week or fortnight — even $50/week compounds materially on typical balances. Enter your average offset balance separately; offset keeps cash liquid while cutting interest. See offset vs redraw if you are unsure which facility you have.

Step 4 — Add an annual lump sum (optional)

Tax refunds and bonuses fit the annual lump sum field — model once a year without changing your weekly budget. EOFY context: tax refund on your mortgage.

Step 5 — Model a rate review last

Tick refinance to a lower rate only as an illustration — the playground compares minimum repayments at the new rate. A rate cut saves interest even if the term looks unchanged; keep paying your old repayment amount after a cut to also shorten the term. The loyalty tax guide covers why this lever often beats tactics.

Fixed-rate borrowers — read this first

Before automating large extras on a fixed loan, check your annual cap (often $10k–$30k). The hub's fixed-rate callout and $50/week extras article explain typical limits — not personal advice.

Cross-check with Moneysmart

ASIC's Moneysmart mortgage calculator and pay off faster guide are useful independent references. Azure Home Loans is not affiliated with ASIC.

Next step

Open the payoff playground, stack the levers you can actually maintain, and email yourself the payoff plan PDF. When the numbers look meaningful, request a 15-minute rate review — general information only, not personal credit advice.