Extra Repayments Calculator: Pay Off Your Mortgage Years Faster

Paying even a modest amount above your minimum home loan repayment compounds faster than most people expect, because every extra dollar stops accruing interest immediately and permanently — which means the following month's interest is calculated on a smaller balance, which frees up slightly more of your payment for principal, and so on for the rest of the loan. Small, consistent extra repayments can cut years off a 30-year loan and save well into six figures in interest.

The 30-second summary

• On a $500,000 loan at 6.00% p.a. over 30 years, an extra $500/month from day one saves ≈$199,500 in interest and pays the loan off 9 years early.
• Even $300/month extra saves ≈$140,800 and finishes the loan 6.25 years early.
• For the same amount, extra repayments and an offset account save almost identical interest — the real difference is access, not maths.
• Most lenders don't automatically lower your minimum repayment once you're ahead — the loan just finishes early instead, unless you ask them to recalculate it.
• Fixed-rate loans usually cap extra repayments (commonly $10,000–$30,000/year) — check before making a large lump sum.

A worked example — $500,000 loan at 6.00% p.a.

Starting point: a $500,000 loan, 30-year term, 6.00% p.a., minimum repayment $2,998/month. Here's what happens if that minimum is topped up from the very first repayment, modelled exactly as the extra repayment calculator does it:

Scenario	Total interest paid	Loan paid off in	Interest saved	Time saved
Minimum repayment only	$579,191	30.0 years	—	—
+$300/month extra	$438,373	23.8 years	$140,818	6.25 years
+$500/month extra	$379,690	21.0 years	$199,501	9.0 years

The pattern to notice: going from $300 to $500 extra a month (a 67% increase in the extra amount) doesn't just proportionally increase the saving — it also compounds faster, because more of every dollar is attacking principal earlier in the loan, when the most interest is normally charged. Starting extra repayments in year one rather than year ten captures most of this effect; the same extra amount started a decade in still helps, just with a smaller total saving since less loan term remains for it to compound over.

Extra repayments vs redraw vs offset — the honest comparison

Most articles present these as three different strategies with three different savings outcomes. For the same dollar amount, that's not quite right — the interest-saving maths is nearly identical across all three. What actually differs is access to the money and, for investors, tax treatment:

	Extra repayments (no redraw)	Extra repayments + redraw	Offset account
Interest saved (same $ amount)	Full saving	Full saving	Full saving
Access to the money	None — it's paid into the loan	Available on request; some lenders apply fees, limits, or delays	Instant, from a normal transaction account
Effect on loan balance	Reduces principal permanently	Reduces principal, redrawable back up	Loan balance untouched on paper
Investment property tax treatment	Reduces the deductible loan permanently	Redrawing to re-borrow can taint deductibility	Safest — the loan itself is never touched
Typical availability	Almost universal	Common on variable loans; check limits	Usually requires a package/fee loan

The practical takeaway: if you're confident you won't need the money back, extra repayments (with or without redraw) and offset are financially close to interchangeable. If there's a real chance you'll want it back — an emergency fund, a future deposit, an investment property — an offset account gives you the same saving with far more flexibility.

Why your minimum repayment usually doesn't change

This surprises a lot of people: making extra repayments on a standard principal & interest loan shortens the loan term, but your contracted minimum monthly repayment typically stays exactly the same. The lender doesn't automatically recalculate a lower minimum just because you're ahead of schedule — you keep paying the original amount, month after month, and the loan simply pays out early instead of running the full term.

If you'd rather lock in a lower ongoing minimum repayment (rather than finishing early while paying the same amount), some lenders will do this on request — often called a loan "recast" or repayment recalculation — but it's not automatic and isn't offered universally. Ask your lender directly if this matters to you.

Watch the fixed-rate cap

Extra repayments are effectively uncapped on most variable-rate loans. Fixed-rate loans are different: most Australian lenders limit additional repayments during the fixed period, commonly to somewhere between $10,000 and $30,000 per year, and paying over the cap can trigger break costs similar to exiting the fixed rate early. If you're on a fixed rate and thinking about a lump sum well above the typical cap, check your product disclosure statement or ask your lender before transferring the money.

Frequently asked questions

Is there a cap on extra mortgage repayments?

Rarely on variable loans. Fixed-rate loans commonly cap additional repayments at $10,000–$30,000 per year, with break costs possible if you exceed it — check your specific loan terms.

Should I make extra repayments or use an offset account?

For the same dollar amount, the interest saving is nearly identical. The real difference is access: offset money stays fully liquid, while extra repayments (without redraw) are effectively gone into the loan. Offset is also the safer choice for investment properties.

Do extra repayments lower my minimum monthly repayment or shorten my loan term?

They shorten the term. Your minimum repayment typically stays the same unless you specifically ask your lender to recalculate it.

What if I need the extra money back later?

Only possible if your loan has a redraw facility, and even then some lenders apply fees, limits, or delays. If there's a real chance you'll want the money back, an offset account is the more flexible option.

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Model your own numbers in the extra repayment calculator, or compare against keeping the same amount in an offset account instead. For every other stage of buying and owning a home, see the full guide to Australian mortgage calculators.

This article provides general information current at July 2026 and does not constitute personal financial advice. Loan terms, redraw availability, and fixed-rate repayment caps vary by lender and product — confirm the specifics with your lender or broker before making extra repayments.