Tip: Press Enter in any input field to calculate quickly.
How to use this GST calculator in Australia
This GST tax calculator is designed for Australian users who want a fast way to work out Goods and Services Tax at the standard rate of 10%. You can use it to:
- Add GST to a GST-exclusive price.
- Remove GST from a GST-inclusive total.
- Find the GST component only from an inclusive amount.
It is useful for quoting jobs, creating invoices, checking supplier bills, and preparing numbers before BAS lodgement.
What is GST in Australia?
GST (Goods and Services Tax) is a broad-based tax of 10% on most goods, services, and other items sold or consumed in Australia. If your business is registered for GST, you generally:
- Charge GST on taxable sales (output tax).
- Claim GST credits for business purchases (input tax credits), where eligible.
- Report and pay the net amount through your Business Activity Statement (BAS).
Not everything attracts GST. Some sales are GST-free or input taxed, which changes how you calculate and report amounts.
GST formulas (simple and practical)
1) Add GST to a GST-exclusive amount
If a price does not include GST:
- GST amount = Exclusive amount × 10%
- GST-inclusive total = Exclusive amount × 1.10
Example: $100.00 ex GST → GST is $10.00 → total is $110.00.
2) Remove GST from a GST-inclusive amount
If a price already includes GST:
- GST-exclusive amount = Inclusive amount ÷ 1.10
- GST amount = Inclusive amount − Exclusive amount
Example: $220.00 inc GST → ex GST is $200.00 → GST is $20.00.
3) GST component from an inclusive amount
A quick shortcut:
- GST component = Inclusive amount × (10 ÷ 110), or simply divide by 11.
Example: $55.00 inc GST → GST component is $5.00.
When to add GST vs remove GST
- Add GST when your quote or product price is shown ex GST and you need the final customer total.
- Remove GST when reviewing a tax invoice that is already GST inclusive and you need pre-tax value.
- GST component only when checking claimable GST or reconciling line items.
Common GST mistakes small businesses make
- Charging GST when the supply is GST-free.
- Assuming every purchase includes claimable GST.
- Using the wrong basis (cash vs accrual) in BAS timing.
- Rounding inconsistently across invoices and accounting software.
- Mixing personal and business expenses, then overclaiming GST credits.
A reliable calculator helps, but your chart of accounts and tax coding in bookkeeping software matter just as much.
GST-free and input-taxed supplies: why this matters
GST-free
GST is charged at 0%, and businesses may still be able to claim GST credits on related purchases. Examples can include certain basic food items, some medical services, and some education-related supplies.
Input-taxed
No GST is charged on the sale, but businesses generally cannot claim GST credits for purchases related to that income. Common examples include many residential rents and many financial supplies.
If you deal with mixed supplies, tax coding can become complex. Consider professional advice when needed.
Quick examples for daily use
Freelancer invoice
You charge $1,500 ex GST for a project. Add GST (10%) = $150. Invoice total = $1,650.
Retail purchase check
A supplier receipt totals $99 inc GST. GST component is $9, and ex GST amount is $90.
Quote comparison
Supplier A quotes $2,200 inc GST. Supplier B quotes $2,000 ex GST. After adding GST, Supplier B total becomes $2,200 — effectively identical.
Frequently asked questions
Is GST always 10% in Australia?
The standard GST rate is 10%, but this calculator lets you change the rate for special scenarios, historical references, or comparison testing.
Can I claim GST on all business expenses?
No. You generally need a valid tax invoice and the purchase must be for business use and eligible under ATO rules.
Should I round GST per line or invoice total?
Many systems round to cents at line level or total level depending on setup. Stay consistent and follow your accounting software + ATO guidance.
Final note
This GST calculator provides quick estimates for everyday finance tasks in Australia. It does not replace legal, tax, or accounting advice. If your situation includes mixed supplies, partial credits, imports, or complex BAS adjustments, speak with a registered tax professional.