GST Calculator
Add GST to a price, strip it out of a GST-inclusive total, or split the tax into CGST, SGST and IGST. Pick a tax slab, add an optional profit margin, and see the net price, the GST amount and the gross total laid out clearly.
Formula
Worked example
Add 18% GST to 100: GST 18, gross 118. Intra-state that is CGST 9 and SGST 9. Remove 18% GST from 118: net = 118 / 1.18 = 100, GST 18. Inter-state the whole 18 is a single IGST.
Adding GST to a net price
Goods and Services Tax (GST) is a broad consumption tax charged as a percentage of a price. To add GST, multiply the net (pre-tax) amount by the rate and add it on: a net price of 100 at 18% gains 18 of GST for a gross price of 118. Equivalently, multiply the net price by (1 + rate), so 100 x 1.18 = 118. If you turn on a profit margin, the calculator first marks up your cost to get the net selling price, then applies GST on top of that, which is how a seller prices a sale from a purchase cost.
Removing GST from a GST-inclusive price
Extracting GST from a tax-inclusive total is the step people most often get wrong. You cannot simply subtract the rate, because the rate was applied to the smaller net figure, not the gross. Instead, divide the gross price by (1 + rate): 118 / 1.18 = 100 net, leaving 18 of GST. At a 10% rate there is a neat shortcut, the GST equals the gross total divided by 11, since 10% of the net is one-eleventh of the gross.
CGST, SGST and IGST
Under India's GST, the same total rate is collected differently depending on where the buyer and seller are. For an intra-state sale (both in the same state) the tax is split into CGST (Central GST) and SGST (State GST), each carrying half the rate, so 18% becomes 9% CGST plus 9% SGST. For an inter-state sale the entire tax is charged as one IGST at the full rate. The total GST is identical either way; only the split and who collects it change. The calculator shows the relevant split automatically once you pick the transaction type.
GST rates and slabs
India uses several slabs (0.25%, 3%, 5%, 12%, 18% and 28%), so the calculator lets you pick a slab directly or enter any custom rate. Other countries run their own single-rate systems: Australia is 10%, New Zealand 15%, Singapore and Canada operate at their own rates. Some goods such as basic food, exports or financial services may be GST-free or exempt. Registered businesses generally claim back the GST they pay on purchases (input tax credits) and remit only the net GST collected, so for them the meaningful cost is the net price.
Common GST rates and slabs
| Region or slab | Rate | Notes |
|---|---|---|
| India, lowest slab | 0.25% | Cut and semi-polished stones |
| India, common slabs | 5%, 12%, 18% | Most goods and services |
| India, highest slab | 28% | Luxury and "sin" goods, often with cess |
| Australia | 10% | Single GST rate |
| New Zealand | 15% | Single GST rate |
| Singapore | 9% | GST (rate as of 2024) |
Indian slabs plus the headline single rates used in nearby GST countries.
Frequently asked questions
How do I remove GST from a total?
Divide the GST-inclusive total by 1 plus the rate as a decimal. For 18% GST, divide by 1.18 to get the net price; the difference is the GST. At 10% you can also just divide the total by 11 to get the GST amount directly.
What is the difference between CGST, SGST and IGST?
On an intra-state sale (buyer and seller in the same state) the GST is split into CGST and SGST, each at half the rate. On an inter-state sale the whole tax is charged as a single IGST at the full rate. The total GST is the same; only the split and the collecting authority differ.
Why can not I just subtract the GST percentage?
Because the GST was calculated on the net price, not the gross. Subtracting 18% of the gross removes too much. Dividing by 1.18 correctly reverses the original calculation and gives the true net amount.
How does the profit margin option work?
In add mode the margin marks up your entered cost to a net selling price first, then GST is applied on top. For example, a cost of 100 with a 20% margin gives a net of 120, and 18% GST on that is 21.60, for a gross of 141.60.