How to calculate GST
Adding GST: GST amount = price × rate ÷ 100; total = price + GST. At 18%, ₹1,000 + ₹180 GST = ₹1,180.
Removing GST: price excluding GST = inclusive price ÷ (1 + rate ÷ 100). From ₹1,180 at 18%: ₹1,180 ÷ 1.18 = ₹1,000, so the GST was ₹180. In Australia the shortcut for 10% GST is to divide the inclusive price by 11 to get the GST.
GST in India: CGST, SGST and IGST
For a sale within the same state, the GST is split equally between the central government (CGST) and the state (SGST, or UTGST in union territories). At 18%, that is 9% CGST + 9% SGST. For a sale to another state (and for imports), the full rate is charged as IGST. The calculator shows both splits.
Since the GST reform effective 22 September 2025, most goods and services fall into two main slabs: 5% (merit rate) and 18% (standard rate), with a special 40% rate for a short list of luxury and sin goods, plus nil-rated and exempt items. Check the rate for your HSN or SAC code before invoicing.
GST rates in other countries
| Country | Rate | Notes |
|---|---|---|
| Australia | 10% | Register when GST turnover reaches A$75,000 |
| New Zealand | 15% | Register when turnover reaches NZ$60,000 |
| Canada | 5% GST or 13–15% HST | HST combines GST and provincial tax: 13% Ontario, 14% Nova Scotia, 15% New Brunswick, Newfoundland and Labrador and PEI; other provinces add PST or QST separately |
| Singapore | 9% | Since 1 January 2024 |
| Malaysia | SST: 5–10% sales tax, 8% service tax (most services) | Malaysia uses SST rather than GST |
Put GST on your invoice
A GST invoice must show your GST number and the GST amount. Use the India GST invoice template (with CGST/SGST or IGST), the Australia tax invoice template or the Canada GST/HST invoice template – or set the tax name to GST in the invoice generator.
General information, not tax advice. Rates and registration thresholds change; confirm them with your tax authority.
Frequently asked questions
How do I calculate 18% GST?
Multiply the price by 0.18 to get the GST and add it on (or multiply by 1.18). To remove 18% GST from an inclusive price, divide by 1.18.
What is the difference between CGST, SGST and IGST?
CGST and SGST are charged together, each at half the rate, on sales within one state. IGST is charged at the full rate on sales between states and on imports.
What are the GST slabs in India now?
Since 22 September 2025 most goods and services are taxed at 5% or 18%, with a 40% rate for a few luxury and sin goods, and some items nil-rated or exempt. Check the specific HSN or SAC code.
How do I remove GST in Australia?
Divide the GST-inclusive price by 11 to get the GST, or divide by 1.1 to get the price excluding GST.
