Add or remove GST/VAT from any amount in seconds. Get the CGST + SGST vs IGST split for India, and a copy-ready invoice line for your bills. Works worldwide — set any tax rate.
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Add GST: total = amount × (1 + rate/100). Remove GST: base = total ÷ (1 + rate/100). For intra-state Indian sales the tax splits equally — 18% becomes 9% CGST + 9% SGST; inter-state sales charge the full 18% as IGST.
GST = base price × rate ÷ 100. For example, 18% on ₹1,000 = ₹180, total ₹1,180. Pick “Add GST” above and enter any rate.
Base = total ÷ (1 + rate ÷ 100). Removing 18% from ₹1,180 gives ₹1,000. Choose “Remove GST” above.
Within one Indian state, GST splits into CGST + SGST (e.g. 18% → 9% + 9%). Between states, the full amount is IGST (18%). This calculator shows both.
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Check the official GST rate schedule against your product's HSN code — most goods fall under 5%, 12%, 18%, or 28%. When in doubt, your supplier's invoice shows the slab they applied, which is usually correct for that item.
Businesses can subtract the GST they paid on purchases from the GST they collect on sales, remitting only the difference to the government. It's the mechanism that prevents tax-on-tax cascading — each stage is effectively taxed only on its own value addition.
GST applies to the transaction value actually paid, so a genuine discount given at or before the sale reduces the taxable amount. Post-sale incentives, free samples, and buy-one-get-one deals have special valuation rules — worth checking with a tax advisor for large amounts.
GST is a value-added tax collected at each stage of the supply chain, but consumers only ever see it in the final price. Every calculation goes one of two directions: adding GST to a tax-exclusive base price, or removing GST from a tax-inclusive total to recover the base and the tax component.
The formulas, with r = GST rate as a decimal: add: total = base × (1 + r); remove: base = total ÷ (1 + r), and GST amount = total − base. Within a state the rate splits into CGST + SGST (e.g. 18% = 9% CGST + 9% SGST); between states it's charged as a single IGST at the full rate.
Worked example: a product priced at ₹1,000 (exclusive) with 18% GST: total = 1000 × 1.18 = ₹1,180 — that's ₹90 CGST + ₹90 SGST on an intra-state sale, or ₹180 IGST inter-state. Reverse: a ₹1,180 inclusive bill → base = 1180 ÷ 1.18 = ₹1,000, so the GST component is exactly ₹180.
Practical tips: common slabs are 5%, 12%, 18%, and 28% — verify your item's slab via its HSN code rather than guessing. Businesses can claim input tax credit on GST paid for purchases, remitting only the difference — which is why GST doesn't cascade like old tax systems. Limitation: composition-scheme dealers, exemptions, and reverse-charge cases follow special rules this math doesn't model.
HSN codes, reverse charge, and e-invoicing: every product maps to an HSN code (services use SAC) that determines its slab — the first 2–4 digits set the category, and misclassification is the most common GST filing error for small businesses. Under the reverse charge mechanism, the buyer (not seller) pays GST on specified goods/services like legal fees and goods transport — if you're the buyer, you owe it even though no GST appears on the invoice. Businesses above the turnover threshold must issue e-invoices with an IRN (Invoice Reference Number) from the government portal; without a valid IRN, your buyer can't claim input tax credit, which makes your invoices worthless to B2B customers. The composition scheme (1–6% flat, no ITC) suits tiny businesses with thin B2B sales — but the moment you sell to GST-registered buyers who need ITC, regular registration pays for itself.