GST Calculator

Exclusive vs inclusive: two different formulas

Adding GST to a tax-exclusive price is a straight percentage:

GST = price × r ÷ 100  ·  gross = price + GST

Removing GST from a tax-inclusive price is where people slip up. The inclusive price is already 100 + r percent of the base, so the tax inside it is:

GST = inclusive price × r ÷ (100 + r)

Taking r% of the inclusive price instead would tax the tax — for an 18% rate the error is almost 3% of the bill.

Worked example (18%)

Add: a base price of 1,000 at 18% gives GST = 1,000 × 18 ÷ 100 = 180, so the invoice total is 1,180. Remove: starting from that inclusive 1,180, GST = 1,180 × 18 ÷ 118 = 180, recovering the 1,000 base exactly. On an intra-state Indian invoice, the 180 is shown as CGST 90 + SGST 90.

India's GST slabs

• 5% — essentials such as packaged food staples, footwear under thresholds, transport services.
• 12% — processed foods, some household goods.
• 18% — the workhorse rate: most services, electronics, restaurant dining (non-luxury).
• 28% — luxury goods, large appliances, automobiles (often plus compensation cess).

CGST, SGST and IGST

Within a state, the GST charge is split 50:50 between central and state governments — 18% billed as 9% CGST + 9% SGST. Across state lines the whole amount is billed as IGST at the full rate; the money is the same, only the ledger changes. The calculator's split row applies to intra-state sales.