How to remove GST from a price
The correct formula for working out the GST inside a total — and why you divide by 11, not take 10% off.
Last updated 3 November 2026
If a price includes GST and you need to pull the GST back out — to fill in a BAS, check an invoice, or claim a credit — there’s one rule to remember: divide by 11. Not take 10% off. Here’s why, and the exact formulas.
The formulas
Australian GST is a flat 10%. Starting from a GST-inclusive total:
- GST amount = total ÷ 11
- Price before GST = total ÷ 1.1
And going the other way, from a price that excludes GST:
- GST amount = price × 0.1
- GST-inclusive total = price × 1.1
Why you divide by 11, not subtract 10%
This is the mistake almost everyone makes. The 10% GST was calculated on the pre-GST price — the smaller number — and then added on. So the GST is 10% of the smaller amount, not 10% of the total.
Take a $110 total:
- Wrong: 10% of $110 = $11. Subtract it and you get $99 — too low.
- Right: $110 ÷ 11 = $10 GST, leaving $100 before GST. Add 10% back ($100 × 1.1) and you’re exactly at $110.
The GST is one-eleventh of any GST-inclusive price, because the total is 11 parts (10 parts price + 1 part GST).
Worked examples
- $55 total: GST = $55 ÷ 11 = $5; price before GST = $50.
- $1,100 total: GST = $1,100 ÷ 11 = $100; price before GST = $1,000.
- $2,497 total: GST = $2,497 ÷ 11 = $227; price before GST = $2,270.
When a price has no GST to remove
Not everything carries GST. Most basic food, many health and medical items, some education, and exports are GST-free, so there’s no 10% inside the price to extract. If an invoice is marked GST-free or shows $0 GST, dividing by 11 would give you a figure that isn’t really there.
Do it instantly
Our GST calculator adds or removes GST and shows the GST amount and the pre-GST price in one step — just enter the total and choose “remove GST”.
Work out your own numbers
Frequently asked questions
How do I remove GST from a total?
Divide the GST-inclusive total by 11 to get the GST amount, or divide by 1.1 to get the price before GST. For $110: GST is $110 ÷ 11 = $10, and the pre-GST price is $110 ÷ 1.1 = $100.
Why do I divide by 11 and not take 10% off?
Because the 10% GST was added to the smaller pre-GST price, not the larger total. Taking 10% off the total removes too much. On a $110 total, 10% off would be $11 (wrong); the actual GST is $10, which is one-eleventh of the total.
How do I add GST to a price?
Multiply the pre-GST price by 1.1, or add 10%. $100 plus GST is $100 × 1.1 = $110.
What is the GST rate in Australia?
GST is a flat 10% on most goods and services. Some items — including most basic food, some health and education, and exports — are GST-free, so no GST is included in their price.