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Mortgage repayment calculator.

See what a home loan will cost you to repay. Enter the loan amount, the interest rate and the term, then choose principal & interest or interest-only. The calculator shows your repayment weekly, fortnightly and monthly, plus the total interest and everything you would repay over the life of the loan.

Weekly and fortnightly repayments are worked out on true 52- and 26-payment schedules, not the monthly amount divided by four or two, which is how lenders quote them.

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How this calculator works.

  1. Principal & interest: each repayment is the fixed amount that pays the loan to zero over the term at the interest rate, using the standard amortisation formula. At 6% over 30 years, every $300,000 borrowed costs about $1,799 a month.
  2. Weekly and fortnightly: each frequency is amortised over its own number of payments (52 or 26 a year) at the annual rate divided by that same number.
  3. Interest-only: the repayment is just the interest, the loan amount times the rate divided by the number of payments a year, so the balance does not fall. When the interest-only years end the loan reverts to principal & interest over the years that remain, and the repayment rises.
  4. Total interest is the total of all repayments over the term, less the amount you borrowed.

What it assumes

  • The interest rate starts at 6.44% (the RBA average new variable rate for Jul 2026, adjusted for the 30 Sep rise). Change it to yours.
  • The rate is held constant for the whole term. A variable rate will move your repayment over time.
  • Fees are not included. To compare loans with fees, use the home loan comparison calculator.
  • Assumptions last reviewed 25 September 2026.

Questions people ask.

How are mortgage repayments calculated?

For a principal & interest loan, the monthly repayment is P × r ÷ (1 − (1 + r)^−n), where P is the amount borrowed, r is the monthly interest rate (the annual rate divided by 12) and n is the number of monthly payments. The same formula works for weekly and fortnightly repayments using 52 or 26 payments a year.

How much interest will I pay over the life of the loan?

On a loan of $500,000 at 6.44% over 30 years, the total interest is about $630,629. A shorter term or a lower rate reduces it sharply, and the calculator shows the effect of each.

Are fortnightly repayments cheaper than monthly?

The fortnightly figure here is a true fortnightly schedule (26 payments a year), which comes out a little under half the monthly amount. Where fortnightly saves interest is when you pay half of your monthly repayment every fortnight: 26 half-payments equal 13 monthly payments, one extra a year, which shortens the loan. The extra repayments calculator shows by how much.

What is the difference between principal & interest and interest-only?

With principal & interest each repayment pays the interest for the period and part of the loan itself, so the balance falls. With interest-only you pay just the interest for a set period, so repayments are lower but the balance stays the same, and the repayment rises when principal & interest starts. The interest-only calculator compares the two side by side.

What happens to my repayments if the interest rate changes?

On a variable rate your lender recalculates your repayment when the rate moves. This calculator holds the rate steady, so to see a different rate, change the interest rate answer. To weigh a fixed rate against a variable one, use the fixed vs variable calculator.

More calculators.

Mortgage Repayment Calculator | Siare