GST Calculator (India)

The GST Council's 56th meeting collapsed the old 5/12/18/28 structure into what the government calls a Simple Tax: a 5% merit rate, an 18% standard rate, and a special 40% demerit rate for a select few goods. Most things that sat at 12% moved down to 5% or up to 18%; most of the 28% slab moved to 18%, with the demerit list going to 40%. The special rates for bullion survived — 3% on gold, silver and jewellery, 0.25% on rough diamonds.

Concretely: everyday essentials like soap, shampoo, toothpaste, butter, cheese, packaged namkeens, bicycles, medicines and medical devices now sit at 5%; air conditioners, televisions of every size, cement, small cars, motorcycles up to 350cc and all auto parts sit at 18%; and pan masala, tobacco products, carbonated drinks, larger cars and SUVs, and motorcycles above 350cc carry 40%. Individual life and health insurance premiums became exempt entirely — one of the reform's most-searched changes. The calculator's rate menu carries the current rates first and keeps 12% and 28% clearly badged as historical, because invoices dated before 22 September 2025 still need them.

Every GST charge is collected as either two taxes or one, and the geography of the sale decides which. When supplier and buyer are in the same state, the rate splits into equal halves: an 18% charge appears as 9% CGST (central) plus 9% SGST (state); a 5% charge as 2.5% + 2.5%; a 40% charge as 20% + 20%. When the supply crosses state lines — or is an import — the full rate is charged once as IGST. The totals are identical either way; what changes is the lines on the invoice and where the revenue flows.

The calculator's inter-state toggle switches between the two presentations. On a ₹10,000 intra-state sale at 18%, it shows CGST ₹900 and SGST ₹900 over a ₹11,800 total; flip the toggle and the same sale shows IGST ₹1,800. Getting the split right matters for invoicing and returns — a common bookkeeping error is recording IGST on a local sale or vice versa, which reconciles painfully later even though the money is the same.

The reverse calculation — what people search as "reverse GST" — answers: this price includes GST, how much is inside? Divide by one plus the rate. A ₹118 receipt at 18% contains ₹118 ÷ 1.18 = ₹100 of base and ₹18 of GST — equivalently, GST = price × 18/118. At 5%, a ₹1,050 bill contains ₹1,000 + ₹50; at 40%, ₹1,400 contains ₹1,000 + ₹400.

The classic error is taking 18% of the inclusive figure: ₹118 × 18% = ₹21.24, which overstates the tax by ₹3.24 because the 18% was charged on the base, not on the total you are holding. The check is the round trip — the correct base, multiplied back by 1.18, reconstructs the receipt exactly. The calculator's extract mode does the division at whichever rate the document carries, including the historical slabs for pre-reform invoices — useful when reconciling expenses that straddle the September 2025 changeover, where the same vendor's receipts legitimately carry different rates either side of the date.

Registration thresholds were untouched by the reform — the Council's own FAQ says so explicitly. Businesses supplying goods register once turnover crosses ₹40 lakh in normal states (₹20 lakh in special-category states); service providers at ₹20 lakh (₹10 lakh special-category). Small businesses under the composition scheme — up to ₹1.5 crore turnover — pay a flat rate (1% for manufacturers and traders, 5% for restaurants) instead of slab-wise GST, and cannot claim input credit. E-invoicing is mandatory for businesses above ₹5 crore annual turnover.

Two traps worth naming. Tobacco and pan masala moved to the 40% slab on 1 February 2026, but a 40%-only calculation understates the real burden — those goods also carry a new central excise duty and health cess, with GST computed on the printed retail sale price rather than the transaction value, so this calculator deliberately does not model tobacco pricing. And for a short list of notified supplies — goods transport agencies, legal services, imported services among them — the reverse-charge mechanism makes the recipient pay the GST directly; the arithmetic here still holds, but who remits it changes. Where a specific item's classification is in doubt, the GST Council's published schedules are the authority.