Mortgage repayments calculator — The Buyers Grail
THE BUYERS GRAIL$119 a property

Calculator

Mortgage repayments calculator

Monthly and weekly principal-and-interest repayments from the price, deposit, rate and term, with the total interest over the life of the loan.

Last updated 15 September 2026 · data vintage Standard amortisation formula; the interest rate is whatever you enter, checked 6 September 2026 · reviewed by The Buyers Grail editorial (agency page text checked 13 September 2026)

Repayments

Enter your figures to see the result.

A repayment figure is the number most buyers feel first: not the price, not the duty, but what leaves the account every month for the next thirty years. This calculator produces it from four inputs and shows the total interest the loan would cost if the rate never moved.

Monthly repayment by interest rate, three loan sizes$400k loan: 5% $2,147, 5.5% $2,271, 6% $2,398, 6.5% $2,528, 7% $2,661; $600k loan: 5% $3,221, 5.5% $3,407, 6% $3,597, 6.5% $3,792, 7% $3,992; $800k loan: 5% $4,295, 5.5% $4,542, 6% $4,796, 6.5% $5,057, 7% $5,322.$0$2k$4k$6k5%5.5%6%6.5%7%$400k loan$400k loan at 5%: $2,147$400k loan at 5.5%: $2,271$400k loan at 6%: $2,398$400k loan at 6.5%: $2,528$400k loan at 7%: $2,661$400k loan$600k loan$600k loan at 5%: $3,221$600k loan at 5.5%: $3,407$600k loan at 6%: $3,597$600k loan at 6.5%: $3,792$600k loan at 7%: $3,992$600k loan$800k loan$800k loan at 5%: $4,295$800k loan at 5.5%: $4,542$800k loan at 6%: $4,796$800k loan at 6.5%: $5,057$800k loan at 7%: $5,322$800k loan
Monthly repayment by interest rate, three loan sizes$400k loan: 5% $2,147, 5.5% $2,271, 6% $2,398, 6.5% $2,528, 7% $2,661; $600k loan: 5% $3,221, 5.5% $3,407, 6% $3,597, 6.5% $3,792, 7% $3,992; $800k loan: 5% $4,295, 5.5% $4,542, 6% $4,796, 6.5% $5,057, 7% $5,322.$0$2k$4k$6k5%5.5%6%6.5%7%$400k loan$400k loan at 5%: $2,147$400k loan at 5.5%: $2,271$400k loan at 6%: $2,398$400k loan at 6.5%: $2,528$400k loan at 7%: $2,661$400k loan$600k loan$600k loan at 5%: $3,221$600k loan at 5.5%: $3,407$600k loan at 6%: $3,597$600k loan at 6.5%: $3,792$600k loan at 7%: $3,992$600k loan$800k loan$800k loan at 5%: $4,295$800k loan at 5.5%: $4,542$800k loan at 6%: $4,796$800k loan at 6.5%: $5,057$800k loan at 7%: $5,322$800k loan
Monthly repayment by interest rate, three loan sizes. Principal-and-interest repayments over 30 years at each rate, from the same formula as the calculator.

How the calculator works

The loan is the price less the deposit. The monthly repayment is the standard principal-and-interest amortisation at the rate and term entered, with the weekly figure derived from the published monthly figure so the two reconcile. Total interest is the monthly repayment multiplied by the number of months, less the amount borrowed.

Reference table

Monthly repayments over 30 years at five rates, for three loan sizes, computed by the same code.

Loan5%5.5%6%6.5%7%
$400,000$2,147$2,271$2,398$2,528$2,661
$600,000$3,221$3,407$3,597$3,792$3,992
$800,000$4,295$4,542$4,796$5,057$5,322

Total interest over the same 30 years:

Loan5%5.5%6%6.5%7%
$400,000$373,024$417,618$463,352$510,177$558,036
$600,000$559,535$626,423$695,028$765,268$837,052
$800,000$746,045$835,232$926,704$1,020,354$1,116,071

What a rate move does

Reading across a row shows it: on the same loan, each half a percentage point changes the monthly figure by an amount most households would notice, and the total interest by far more. Lenders test applications at a rate 3 percentage points above the one offered for this reason, and the borrowing capacity calculator applies the same buffer.

What the figure leaves out

Fees, offset and redraw arrangements, fixed-rate periods, interest-only periods and rate changes over the term are not modelled. The figure assumes the rate entered applies for the whole term, which it will not.

Where the report fits

The repayment follows from the price. The report's fair-value range is about whether the price is the right one to be repaying in the first place.

Sources

  1. Reserve Bank of Australia, interest rates statistics (lenders' rates) — checked 6 September 2026
  2. APRA, loan serviceability buffer of at least 3.0 percentage points above the loan product rate (October 2021 letter to ADIs) — checked 13 September 2026. For the current rate environment; the calculator applies the rate you enter. Open before the page is indexed.

Last updated 15 September 2026 · reviewed by The Buyers Grail editorial (agency page text checked 13 September 2026).

Related

Where the report fits

A Property Decision Report does this work for one property you're weighing up: the fair-value range built from recorded comparable sales, where the asking price sits against it, the vendor and agent read, the risks that matter, and your opening, target and walk-away numbers, in writing, within 24 hours.

Get a report — $119 Free address check first Message Theo on WhatsApp

Every pack is the same full report; only the number of properties changes. $249 for three properties, $349 for five.