Calculators · Practical tutorial

How to add or extract Indian GST from a price

Worked arithmetic examples for GST-exclusive and GST-inclusive amounts, with intra-state and inter-state tax distinctions.

Published 27 October 2026 · CraftAI editorial guide

Open Indian GST Calculator →

Two different GST questions

When a quoted price excludes GST, tax is added to the base amount. When a price already includes GST, the tax portion must be extracted instead. Mixing these two calculations is a common reason that totals do not reconcile.

Adding GST to a base amount

For a hypothetical taxable base of ₹1,000 and an illustrative 18% GST rate, tax is ₹1,000 × 0.18 = ₹180. The final price is ₹1,180. For an intra-state supply in a situation where 18% GST applies, the tax is typically split as ₹90 CGST and ₹90 SGST; for a qualifying inter-state supply the tax would generally be ₹180 IGST.

Extracting included GST

If the price is already ₹1,180 including 18% GST, the base amount is ₹1,180 ÷ 1.18 = ₹1,000. The included tax is ₹1,180 − ₹1,000 = ₹180. Subtracting 18% of ₹1,180 directly would be incorrect because the percentage applies to the pre-tax base.

Apply this in the CraftAI tool

1. Open the Indian GST Calculator.
2. Enter the price and rate that actually apply to the transaction.
3. Choose whether the input is exclusive or inclusive of GST, and select the supply type where offered.
4. Compare the tool's base, tax and total values against the formula above.

Important tax limits

This is a mathematical example, not tax advice. Tax rates, exemptions, transaction type, place-of-supply rules and invoicing requirements matter. Verify current treatment on official GST resources or with a qualified adviser before issuing invoices.

Why might my figure differ by a paisa?

Rounding conventions can produce minor differences between individual tax components and the combined amount. Follow applicable invoicing and rounding rules for your situation.