How to use the GST calculator
- Enter the Amount you have — a price before or after GST.
- Enter the GST rate — the percentage charged where you are (for example 5%, 10%, 12%, 18% or 28%).
- Read the result. The GST to add, the gross price, the GST included, and the net price all update as you type.
Worked example
On a $1,000 net amount at 10% GST, the GST to add is $100 and the gross price is $1,100. If instead your $1,100 already includes GST, the GST built into it is $100 and the net price is $1,000 — the same two figures, read from the other direction.
The formula
GST added = Amount × rate ÷ 100
Gross = Amount + GST added
GST included = Amount × rate ÷ (100 + rate)
The calculator shows both directions at once. If your amount is exclusive of GST, use the "GST to add" and "Gross price" figures. If your amount is GST-inclusive, use the "GST included" and "Net price" figures. The inclusive math divides by (100 + rate), not by 100 — that is the step many people get wrong.
What GST rate should I use?
GST (Goods and Services Tax) is a consumption tax used in many countries, and the rate depends on both the country and the type of goods or service:
- India — a four-slab system of 5%, 12%, 18% and 28%, with some essentials at 0%.
- Australia — a single 10% GST on most goods and services.
- Canada — 5% federal GST; provinces add their own tax, so the combined rate is often 12%–15% (HST).
- Singapore — 9% GST, rising in steps in recent years.
- New Zealand — 15% GST on almost everything.
Check the rate that applies to your specific item — some goods (food, medical supplies) are exempt or zero-rated in many jurisdictions.
GST vs VAT
GST and VAT are the same kind of tax: a consumption tax added to the price at each stage of production, with the end consumer bearing the cost. The name differs by country — "GST" is used across the Commonwealth, while "VAT" is common in Europe and elsewhere. This calculator works for either; just enter the rate that applies to you.