Reverse GST Calculator (Remove GST)
Enter a price that already includes GST to see how much GST is in it and what the price was before GST.
Take GST out of a price
Dollars and cents, for example 1,250.50
Why you divide by 11, not by 10
A GST-inclusive price is the pre-GST price plus 10% of it, which is 1.1 times the pre-GST price. Going backwards, you divide by 1.1. The GST itself is the pre-GST price × 0.1, which works out to the inclusive price ÷ 11.
GST = price including GST ÷ 11
Price excluding GST = price including GST − GST
A common mistake is taking 10% off the total. 10% of $110.00 is $11.00, which would leave $99.00. The correct figures are $10.00 of GST and a $100.00 price before GST.
Worked example with rounding
A supplier quotes $1,000.00 including GST. The GST is $1,000.00 ÷ 11 = $90.9090…, which rounds to $90.91. The price excluding GST is $1,000.00 − $90.91 = $909.09. Working out the pre-GST price as the total minus the rounded GST keeps the two parts adding back to exactly $1,000.00.
GST inside common prices
All amounts include GST. The $82.50 row matters when you buy for a business: for a purchase above $82.50 (including GST) you need a tax invoice to claim the GST credit.
| Price including GST | GST (1/11) | Price excluding GST |
|---|---|---|
| $11.00 | $1.00 | $10.00 |
| $55.00 | $5.00 | $50.00 |
| $82.50 | $7.50 | $75.00 |
| $110.00 | $10.00 | $100.00 |
| $220.00 | $20.00 | $200.00 |
| $550.00 | $50.00 | $500.00 |
| $1,100.00 | $100.00 | $1,000.00 |
| $2,200.00 | $200.00 | $2,000.00 |
| $11,000.00 | $1,000.00 | $10,000.00 |
When you need to take GST out
- Recording a purchase. Books and spreadsheets usually track the price before GST and the GST separately, so a receipt that shows only the total needs splitting.
- Claiming GST credits. Registered businesses claim the GST in the price of what they buy for the business. The GST is one eleventh of the price when the whole price is taxable.
- Completing a BAS. Under the ATO’s calculation worksheet method, GST-inclusive sales and purchases are divided by 11 to get 1A and 1B. The BAS calculator does the steps.
- Comparing quotes. One supplier quotes ex GST and another inc GST. Strip the GST out of the second to compare like with like.
Frequently asked questions
How do I take GST out of a price?
Divide the GST-inclusive price by 11 to get the GST, then subtract it from the price. For $110.00: $110.00 ÷ 11 = $10.00 GST, and $110.00 − $10.00 = $100.00. You can also divide the price by 1.1 to get the price before GST in one step.
How much GST is in $100?
If $100.00 already includes GST, the GST is $100.00 ÷ 11 = $9.09 (rounded from $9.0909…) and the price before GST is $90.91. If $100.00 is the price before GST, the GST is $10.00; use the add GST calculator for that.
Why can’t I just take 10% off the total?
Because the 10% was added to the smaller, pre-GST price. Taking 10% off $110.00 leaves $99.00, which is $1.00 too low. Dividing by 1.1 gives the correct $100.00.
Can I divide by 11 if some items on the invoice are GST-free?
Only for the part of the total that includes GST. GST-free items carry no GST, so dividing the whole invoice total by 11 overstates the GST. Enter each item separately in the invoice GST calculator and mark the GST-free ones.
What formula do I use in Excel or Google Sheets?
With the GST-inclusive price in A2, =A2/11 gives the GST and =A2/1.1 gives the price before GST. The guide has formulas with rounding.
Is the GST on a tax invoice always one eleventh of the total?
Only when the whole price is taxable. If an invoice has GST-free items, the GST is less than one eleventh of the total. The ATO allows a tax invoice to say “Total price includes GST” instead of showing the GST amount, but only if the GST is exactly 1/11 of the total price.
Sources
- ATO: Tax invoices (the “Total price includes GST” statement and the $82.50 threshold)
- ATO: BAS and GST tips (holding tax invoices to claim GST credits)
- ATO: Step 4, calculating purchases using the calculation worksheet (divide GST-inclusive purchases by 11)
- ATO: How GST works
General information only, not tax advice. Check your situation with the ATO or a registered tax or BAS agent.