GST Calculator
Add or remove Goods and Services Tax at any rate for invoices and receipts.
What it does
Goods and services tax is a consumption tax collected in stages and paid in full by the final buyer. Shops in most countries print gross prices with GST already inside, while business quotes often show net prices with GST added at the end, which is why both directions matter.
The tool above converts either way at any rate you set. Pick net to gross when you quote work or check a supplier line, and gross to net when you read a receipt and want the pre tax price or the tax slice alone.
The math is simple but easy to flip. Adding 10% multiplies by 1.10, while removing 10% divides by 1.10 instead of subtracting 10% straight off the gross. The second error understates the net by several dollars on every hundred.
Rates move by place. Australia and New Zealand use 10%, Canada uses 5% federal plus provincial rates, and Singapore uses 9%. Always check the current schedule for your country before invoicing.
How to use
- Pick the direction first: net to gross adds GST, gross to net strips it.
- Enter the amount in your currency. Net means before tax, gross means tax included.
- Enter the GST rate as a percent, for example 10 for 10%.
- Read the converted amount plus the GST slice and the entered value for the audit trail.
- Flip the direction to cross check: converting back should return the start within a cent.
Formula
- net
- Price before GST, used between businesses.
- gross
- Price with GST inside, printed on receipts.
- rate
- GST percent for the country.
Zero rates still enter as 0, giving identical net and gross with zero tax. Rounding happens once at the end per line in most tax rules, so converting line by line can differ by a cent from converting a rounded total.
Worked example
Example: $100 net at 10% GST
Net price 100, GST rate 10%, direction net to gross.
- Rate as a factor: 10 / 100 = 0.10, plus one is 1.10.
- GST slice: 100 x 0.10 = $10.00.
- Gross: 100 + 10 = $110.00.
- Tool shows result $110.00, GST $10.00, entered $100.00.
- Reverse check: 110 / 1.10 = $100.00 net, which closes the loop.
Reference table
| Place | Standard rate | Net 100 becomes |
|---|---|---|
| Australia | 10% | $110.00 gross |
| New Zealand | 15% | $115.00 gross |
| Canada federal | 5% | $105.00 gross |
| Singapore | 9% | $109.00 gross |
Limits
- Rate schedules change, so confirm the live rate for your country.
- Zero rated and exempt treatments differ by product and need separate lines.
- Currency conversion and card fees sit outside this math.
- US sales tax works differently (added at register, varies by state) and needs its own page.
Common mistakes
- Subtracting 10% from the gross to remove 10% GST, which gives $99 instead of $100 on $110.
- Applying the standard rate to zero rated or exempt goods.
- Rounding the rate factor mid chain instead of once at the end.
- Mixing net and gross lines on one invoice without labels.
- Using last year rate after a budget change.
Try it yourself
Quick checks. Answers sit tucked under each question.
Net $50 at 10%?
GST $5.00, gross $55.00 (50 x 1.10).
Gross $220 holds what GST at 10%?
Net $200.00, GST $20.00 (220 / 1.10 = 200).
Net $200 at 15%?
GST $30.00, gross $230.00.
Questions
How do I add 10% GST?
Multiply the net by 1.10. A $100 net becomes $110 gross with $10 tax.
How do I remove GST from a gross price?
Divide by 1 plus the rate. At 10%, $110 / 1.10 = $100 net.
Why is removing GST not the same as subtracting the percent?
The percent applies to the net base. Subtracting 10% from $110 gives $99, while the true net is $100.
What rate should I use?
The rate for your country. Australia and New Zealand use 10%, Canada 5% federal, Singapore 9%.
Is GST the same as VAT?
They work the same way, a tax added at each stage and borne by the final buyer. Names and rates differ by country.
What does zero rated mean?
Taxable at 0%: no tax is charged but the seller can still reclaim input tax, unlike exempt sales.