GST Calculator
Add GST to a price, or pull it back out of an inclusive one.
About this calculator
This GST calculator handles both jobs an Indian invoice throws at you: adding GST to a base (GST-exclusive) price to find what the customer pays, and removing GST from an inclusive price to find how much of a bill is tax. Pick a slab — 5%, 12%, 18% or 28% — or type any custom rate, and it shows the base amount, the GST amount and the total, plus the equal CGST/SGST split used on intra-state invoices.
Removing GST is the step people get wrong by hand: subtracting 18% from an inclusive price overshoots, because the tax was charged on the smaller base amount, not on the inclusive total. The calculator divides by 1.18 instead, which is the correct reverse ('back-calculate the GST') method.
Frequently asked questions
How do I calculate GST in India?
To add GST, multiply the base price by the rate and divide by 100, then add it on: a ₹1,000 service at 18% GST is 1,000 + 180 = ₹1,180. The calculator's 'Add GST' mode does this for any slab or custom rate.
How do I remove GST from a GST-inclusive price?
Divide the inclusive price by (1 + rate ÷ 100). For ₹1,180 at 18%, the base is 1,180 ÷ 1.18 = ₹1,000 and the GST portion is ₹180. Subtracting 18% of 1,180 would give the wrong answer, because GST was charged on the base, not the total. This reverse calculation is what the 'Remove GST' mode does.
What is the difference between a GST-inclusive and GST-exclusive price?
A GST-exclusive price is the base amount before tax — what a seller quotes before adding GST. A GST-inclusive price already has GST folded in, which is what you're actually charged. The same ₹1,000 base becomes a ₹1,180 inclusive price at 18% GST; 'Add GST' goes exclusive → inclusive, and 'Remove GST' goes the other way.
What are the common GST slabs in India?
Most goods and services fall under 5%, 12%, 18% or 28%, with 18% the most common rate for services; some essentials are taxed at 0%. Rates are set by the GST Council and do change, so check the current rate for your specific item — the calculator accepts any custom percentage.
What is the CGST and SGST split?
On a sale within one state, GST is collected as two equal halves: central GST and state GST. An 18% invoice is billed as 9% CGST + 9% SGST, which is why invoices show two tax lines. The calculator shows this equal split for the rate you choose.
What is IGST, and how is it different from CGST/SGST?
IGST (Integrated GST) applies to inter-state supplies — where the seller and the buyer are in different states — and is charged as one single tax equal to the full rate, rather than split in half. An 18% inter-state invoice shows 18% IGST as one line; the same 18% on an intra-state invoice shows as 9% CGST + 9% SGST. Either way, the total tax charged is the same 18% — only how it's split between the tax lines changes.