Whether you're pricing a product, checking a supplier's bill, or preparing an invoice, GST math comes up daily. Here are the exact formulas with worked examples, updated for the current GST 2.0 slabs.
How do you calculate GST on a price?
GST amount = (Base Price × GST Rate) ÷ 100. Example: on a ₹10,000 item at 18%, GST is ₹1,800 and the final price is ₹11,800. Within the same state this splits into CGST ₹900 + SGST ₹900; across states it's IGST ₹1,800.
How do you remove GST from an inclusive price?
Base Price = Inclusive Price × 100 ÷ (100 + GST Rate). Example: ₹11,800 inclusive at 18% gives a base of ₹10,000 and GST of ₹1,800. This 'reverse GST calculation' is what you need when a customer quotes you a final price.
Current GST rates in India (2026)
- 0% — essential items (unbranded food grains, fresh produce, books)
- 5% — mass-consumption goods and most items moved down from the old 12% slab
- 18% — the standard rate for most goods and services, including former 28% consumer durables
- 40% — luxury and sin goods only (tobacco, pan masala, aerated drinks, luxury cars)
- Special rates: 3% on gold and jewellery, 0.25% on rough diamonds
CGST, SGST and IGST — which applies?
It depends on the place of supply. Sale within your own state: half CGST + half SGST. Sale to another state: full IGST. The total tax is identical — only the split changes — but reporting it wrongly causes mismatches in your GSTR-1.
Skip the manual math
Use our free GST calculator at bizgstpro.com/tools/gst-calculator for instant results, or let BizGST Pro calculate the correct split automatically on every invoice you create.