How to use this GST calculator
- Enter the amount. Type the price you are starting from, e.g. 100. The currency does not matter, the calculator works with the plain number.
- Enter the GST rate. Type the percentage that applies, such as 18 for a common Indian slab, or use a quick-pick button for 5, 12, 18, 28 or 10.
- Pick add or remove. Choose "Add GST" when your price is net (before GST) and you want the total, or "Remove GST" when your price already includes GST and you want to pull it back out.
- Read the three cards. Net is the price excluding GST, GST amount is the GST portion, and Gross is the full GST-inclusive total. They recalculate instantly as you type.
Nothing is submitted or stored: the numbers never leave your device, so you can check quotes, receipts and invoices privately.
How GST is added and removed
GST is a flat percentage applied to a price, so two small formulas cover every case. To add GST to a net price: GST = net × (rate ÷ 100) and gross = net × (1 + rate ÷ 100). With a net of 100 at 18%, that is 100 × 0.18 = 18 GST and a 118 gross.
To remove GST that is already inside a gross price, you cannot simply take the percentage of the gross, you have to divide it out: net = gross ÷ (1 + rate ÷ 100), then GST = gross − net. For a gross of 118 at 18%, that is 118 ÷ 1.18 = 100 net and 18 GST. A common mistake is taking 18% of 118, which overstates the GST, because the 18% was charged on the net 100, not the 118 total.
GST rates differ by country
GST is the same idea everywhere, a flat percentage added to goods and services, but the rate is not. So type the rate that applies where you are and this tool handles the rest. Common rates include:
- India: slabs of 5, 12, 18 and 28 percent depending on the item.
- Australia: a single 10 percent rate on most goods and services.
- New Zealand: 15 percent.
- Singapore: 9 percent.
The quick-pick buttons cover the four Indian slabs plus Australia's 10 percent, but you can type any rate, including decimals, if yours differs.
Common real-world uses
- Quoting a client: add GST to a net fee so you can show the all-in price.
- Reading a receipt: remove the GST from a gross total to see exactly how much was GST.
- Bookkeeping: split a GST-inclusive expense into its net and GST parts for your records.
- Pricing products: work backwards from a target shelf price to the net amount you actually keep.
Frequently asked questions
How do I add GST to a net price?
Pick "Add GST (amount is net)", enter the net price and the rate, and the calculator multiplies the price by the rate to get the GST, then adds it on. For example, 18% GST on 100 gives 18 in GST and a 118 gross total.
How do I remove GST from a gross price?
Choose "Remove GST (amount is gross)" and enter the GST-inclusive price. The calculator divides by 1 plus the rate to recover the net, then shows the GST that was included. A 118 price at 18% gives a 100 net and 18 of GST.
What GST rate should I use?
It depends on your country. India uses 5, 12, 18 and 28 percent slabs, Australia uses 10 percent, New Zealand 15 percent and Singapore 9 percent. Type whichever rate applies to you.
Does it handle decimal rates?
Yes. Both the amount and the rate accept decimals, so unusual rates and prices like 19.99 work perfectly. Results are rounded to two decimal places for display.
Which currency does it use?
None in particular, it is currency-neutral. Whatever number you enter is treated as a plain amount, so the net, GST and gross all come out in the same currency you typed.
Results are rounded for display; for invoices, filings or accounting, double-check critical figures against official GST rates.