GST calculator

What the result means

Australian GST is a flat 10% tax on most goods and services. Adding GST increases an exclusive price by 10%. Removing GST finds the 1/11 component already inside an inclusive price.

How it is calculated

Add: GST = amount × 10%. Remove: GST = inclusive amount ÷ 11

• Amount: Exclusive price when adding GST; inclusive price when removing GST.
• GST rate: 10% for a standard Australian taxable supply.

Adding GST multiplies the exclusive amount by 1.1. Removing GST divides the inclusive amount by 11 to isolate GST, then subtracts that from the inclusive amount to recover the exclusive price.

Worked example

Adding GST to a $1,250 invoice

A consultant invoices $1,250 plus GST for a taxable supply.

GST

$1,250 × 10% = $125.00

Total

$1,250 + $125 = $1,375.00

Check

$1,375 ÷ 11 = $125.00 GST

The tax invoice should show $1,250 exclusive, $125 GST and $1,375 inclusive.

Why inclusive GST is 1/11, not 10% of the total

If a $100 item has 10% GST added, the customer pays $110. The GST in that $110 is $10, which is one eleventh of the inclusive amount — not 10% of $110 ($11). Using 10% of an inclusive price overstates GST.

Some groceries, medical services, education and exports are GST-free. Input-taxed supplies such as most residential rent and financial services do not add GST in the same way. This calculator is for standard taxable supplies at 10%.

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