Total Interest on a $600k Home Loan Over 30 Years
Published 31 May 2026
The short answer
On a $600,000 home loan at 6% p.a. over 30 years with principal-and-interest repayments, you'll pay roughly $695,000 in total interest, which is more than the amount you borrowed. Your monthly repayment is about $3,597, and across 360 payments you repay around $1.295 million in total ($600,000 principal plus ~$695,000 interest). The exact figure moves with your interest rate, so a higher or lower rate changes the total interest substantially.
How total interest works on an Australian home loan
Australian lenders amortise your loan: each repayment covers the interest accrued for that period first, and whatever is left chips away at the principal. Interest is typically calculated daily on your outstanding balance and charged monthly, using the actual number of days in each period (see Moneysmart's mortgage calculator).
Early on, almost all of your repayment is interest because the balance is large. As the principal slowly falls, more of each repayment goes to principal, which is why total interest is so front-loaded over 30 years. Three things drive the total:
- Interest rate is the single biggest lever. Every extra 0.5% on a $600k loan adds tens of thousands over the life of the loan.
- Loan term: a longer term means lower repayments but far more interest.
- Repayment behaviour: extra repayments and a sustained offset balance both cut total interest and shorten the term.
As context, the RBA's lenders' interest rates show owner-occupier variable rates have sat broadly in the high-5% to mid-6% range through the 2025–26 financial year, so 6% is a reasonable illustrative rate.
Worked example: $600,000 at 6% over 30 years
The standard amortisation formula gives the repayment, then total interest is repayments × number of periods − principal.
| Item | Value |
|---|---|
| Loan amount | $600,000 |
| Interest rate | 6.00% p.a. |
| Term | 30 years (360 monthly payments) |
| Monthly repayment | ~$3,597 |
| Total repaid | ~$1,295,000 |
| Total interest | ~$695,000 |
How the rate changes things (same $600k, 30 years):
| Rate | Monthly repayment | Total interest |
|---|---|---|
| 5.0% | ~$3,221 | ~$559,000 |
| 6.0% | ~$3,597 | ~$695,000 |
| 7.0% | ~$3,992 | ~$837,000 |
Repayment frequency matters too. Switching to true fortnightly repayments of ~$1,659 (half the monthly amount, paid 26 times a year) means you pay slightly more each year, which nudges total interest down. And paying more than half the monthly figure each fortnight clears the loan years early.
Now add an extra $200/month on top of the $3,597 P&I repayment: the loan is gone in about 26 years instead of 30, and total interest drops to roughly $588,000, a saving of about $107,000. That's what attacking the principal early does.
Model this in True Loan
Open True Loan and set:
- Loan amount: 600,000
- Interest rate: your rate (try 6%)
- Term: 30 years
- Repayment type: Principal & interest
- Frequency: Monthly (or try Fortnightly to compare)
True Loan instantly shows your repayment, total interest, and total cost over the life of the loan, plus a timeline of your remaining debt. To see how to pay less interest, use the two dedicated inputs:
- Extra repayment ($/month): add, say, 200 to see the term and total interest shrink.
- Offset balance: enter a sustained offset amount, and interest accrues on the loan minus the offset, so a steady balance clears the loan early.
Want to weigh two rates or terms head-to-head? Use the side-by-side comparison. For the deeper dives, see how much an offset saves on a $600k loan, how much extra per month pays it off sooner, and 25 vs 30 years.
Common questions and mistakes
Why is the interest almost as much as the loan? Over 30 years at 6%, the front-loaded interest stacks up. It's normal for total interest to approach or exceed the principal on long terms.
Does a lower rate or extra repayments save more? Both help. A lower rate reduces interest on every dollar; extra repayments and offset reduce the balance interest is charged on. The Moneysmart guide to paying off your mortgage faster explains the levers.
Is this the same as the comparison rate? No. The comparison rate folds in fees to help compare products; the figures here are pure interest on the loan balance.
Will my repayment change? On a variable loan, yes: when your rate moves, so does your repayment (or term), and so does total interest.
These are estimates for general information only, not financial or credit advice. Check your actual rate and the official sources linked above, and confirm figures with your lender.
This guide is general information and estimates only — not financial or credit advice. Figures vary by lender and circumstances; always confirm with official sources.