About this tool
Since 22 September 2025 most goods and services fall in the 5% or 18% GST slab, with 40% for a short list of luxury and sin goods. Older 12% and 28% rates are included for invoices from before the change.
Adding and removing GST without mistakes
GST errors usually come from one of two places: adding tax to a price that already includes it, or working out the tax on the wrong base when removing it. To add GST, multiply the base price by the rate. To remove it from a price that already includes GST, divide by one plus the rate rather than subtracting the percentage. A bill of ₹1,180 at 18% has a base of ₹1,000 and GST of ₹180, not ₹212.
The split between central and state tax depends on where the supply happens. For a sale within the same state, the GST is divided equally into CGST and SGST, so the ₹180 above becomes ₹90 each. For a sale to another state, the whole amount is charged as IGST. This calculator shows both splits so you can fill in an invoice correctly.
The GST rate overhaul of September 2025 moved most items into two main slabs, 5% and 18%, and created a separate 40% rate for a small group of luxury and sin goods. The calculator still offers the earlier 12% and 28% rates, since you may need them when checking or correcting bills issued before the overhaul. If you are a small business, keep the GST you collect separate from your own revenue, since it belongs to the government and has to be paid when you file your return. When in doubt about the correct rate for a product, check its HSN or SAC code against the official rate list before you issue the invoice.
How to use it
- Enter your numbers in the boxes, or drag the sliders.
- Read the result on the right. It updates as you type.
- Open the year-by-year table, if shown, to see how the numbers change over time.
- Use 'Copy link with these values' to save the calculation or send it to someone.
Questions
How do I remove GST from an inclusive price?
GST amount = Price × Rate ÷ (100 + Rate). For ₹1,180 at 18%, GST is ₹180 and the base price is ₹1,000.
When is it CGST + SGST and when IGST?
Within the same state the tax is split equally into CGST and SGST. For a sale to another state, the full amount is IGST.
Last reviewed 16 October 2026. Results are estimates for planning. Check important figures with your bank, employer or a qualified adviser.