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Mortgage Repayment Calculator Australia

Estimate weekly, fortnightly and monthly repayments in Australia. Add an offset balance, extra repayments or an interest-only period to see your repayment now, likely step-up after IO ends, and your estimated time + interest saved.

General information only (not financial advice). Calculations are indicative and may differ from lender systems due to rounding, fee handling and daily-interest methods.

Last updated: 4 February 2026

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Rate Challenge — Mortgage Repayment Calculator

Indicative only; fees and lender policy vary. No broker fee on standard home loans.
What this calculator shows (that most don’t)

Model offset + extra repayments + the interest-only “step-up”

Many tools show a single repayment. This one helps you estimate the repayment now, what it could become after an interest-only period ends, and how an offset or extra repayments may change the timeline and total interest.

Show details & quick answers
  • True weekly / fortnightly / monthly repayments (52/26 periods, not a simple divide)
  • Interest-only repayment (offset-aware) and an estimated repayment after IO ends
  • Estimated years + interest saved when you add extra repayments and/or an offset
Quick answers: Repayment formula Offset vs extra Why repayments jump after IO Weekly vs monthly How repayments work
Tip: enter the loan amount after any deposit/LMI capitalisation.
Variable or fixed—use your best estimate.
Select 1–40 years (default 30).
We also show monthly/fortnightly/weekly for comparison.
Interest-only keeps the balance higher, so total interest is usually higher over time.
If you choose interest-only, repayments usually jump after the IO period ends.
For fixed loans, extra repayments may be capped—check your product rules.
Offset reduces the interest-charging balance (daily in most lender systems).
Status: Ready
Assumptions: We use standard amortisation for P&I. Weekly/fortnightly use true 52/26 periods. Offset is modelled as a reduction to the interest-charging balance each period (conservative). Lenders can differ slightly due to daily interest, rounding and fees.

Your results

Repayment — Monthly

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Repayment — Fortnightly

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Repayment — Weekly

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Total interest (baseline)

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Assumes monthly P&I for the entire term

Selected frequency payment

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Per selected period, incl. extra

Time & interest saved

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vs baseline schedule
Important: If you select interest-only, we calculate the IO repayment as the net interest (offset-aware) during the IO period. When IO ends, we recalculate the P&I repayment over the remaining term, which is why repayments usually jump.

Next steps

If your repayments feel tight (or you want to pay the loan off sooner), the fastest win is usually a quick rate check and a strategy chat. Here are the most useful tools and guides to take the next step.

Check your rate

Compare your current rate and see whether a refinance could reduce repayments or total interest.

Home Loan Interest Rate Review Calculator → Home Loan Refinance Guide →

Plan your borrowing

Use complementary calculators and guides to sanity-check your borrowing power and next move.

Max Borrowing Calculator → Rentvesting Calculator → All calculators →

Speak with a broker

Get a tailored comparison across 35+ lenders and a clear plan for repayments, offsets and refinance timing.

Free Mortgage Broker (Australia-wide) → Contact Rate Challenge → Mortgage Broker Melbourne →
Prefer to learn first? Start here: Home Loan Guide and for first-time buyers: First Home Buyer Guide.

How mortgage repayments work in Australia

In Australia, most home loans calculate interest on a daily basis and charge it monthly (even if you pay weekly or fortnightly). This calculator uses standard amortisation for P&I and a conservative offset model. Small differences between lenders can occur due to rounding and fee handling.

Principal & Interest (P&I)

Repayments cover interest + principal, so your balance reduces over time.

Interest-only (IO)

Repayments generally cover net interest only during the IO period. When IO ends, repayments usually increase.

Offset vs extra repayments

An offset account reduces the interest-charging balance while keeping funds accessible. Extra repayments reduce principal and can shorten the term. On fixed rates, extra repayments may be capped.

Want the “big picture”? See the Home Loan Guide. First time buying? Start with the First Home Buyer Guide.

Mortgage repayment calculator — FAQs

Quick answers about repayments, interest-only periods, offsets, extra repayments and how lenders can differ.

How are mortgage repayments calculated?
We estimate repayments using the standard amortisation formula. P&I repayments include interest and principal. Interest-only repayments cover net interest during the IO period (offset-aware). When IO ends, repayments usually increase because the balance is repaid over the remaining term.
Weekly/fortnightly repayments cheaper than monthly?
Often, yes—because repayments are made more frequently and can reduce interest slightly. Some lenders pro-rate weekly/fortnightly from a monthly amount, so results can vary. This calculator uses true 52/26 payment periods per year.
Why does my repayment jump after the IO period?
During IO, the balance usually doesn’t reduce (unless you add extra repayments). When IO ends, you repay the remaining balance over the remaining term, so the P&I repayment is typically higher.
Offset vs extra repayments — what’s the difference?
Offset reduces the interest-charging balance while funds remain accessible. Extra repayments reduce principal directly and can shorten the term. Tax treatment can differ for investment loans—confirm with your accountant where relevant.
What fees and charges are excluded?
Results are indicative and exclude lender application fees, package fees, settlement costs, LMI, government charges and break costs on fixed loans. We’ll provide a tailored credit quote with full fees once you choose an option.
What should I do if my repayments feel too high?
Start by checking your current rate and loan features (offset/redraw, fixed/variable split). Then compare alternatives. Use the Rate Review Calculator and Refinance Guide, or speak with a broker for a comparison across 35+ lenders.
Related tools: Rate Review Calculator · Max Borrowing Calculator · Rentvesting Calculator ·
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