What is a GST Calculator?
GST (Goods and Services Tax) is India’s unified indirect tax, charged as a percentage of the transaction value at the applicable slab rate for that good or service. Following the GST 2.0 rate rationalisation, most goods and services now fall under a simplified 5% or 18% structure, with a 40% rate reserved for select luxury and "sin" goods.
Switch between adding GST to a base price (exclusive) or extracting the base amount from a price that already includes GST (inclusive) — the two calculations aren’t just mirror images of each other, so it’s easy to get wrong by hand.
How each mode is calculated
In inclusive mode, dividing (not simply subtracting the percentage) is what correctly reverses out the GST, since the rate was originally applied to the smaller base amount, not the larger inclusive one.
Frequently asked questions
What are the current GST slabs?
Following the GST 2.0 reform, the main slabs are 0% (exempt items) and two standard rates of 5% and 18%, with a special 40% rate for select luxury and sin goods — down from the earlier four-slab structure. Always check the applicable rate for your specific good or service, since exceptions exist.
Why can’t I just subtract 18% to remove GST from an inclusive price?
Because 18% was calculated on the smaller base amount, not on the larger GST-inclusive total — subtracting 18% of the inclusive price removes too much. Dividing by (1 + rate) is the correct way to reverse it.
Does this calculate CGST and SGST separately?
No — it shows the total GST amount. For an intra-state sale, that total is typically split evenly into CGST and SGST (half each); for an inter-state sale, the full amount is charged as IGST.