GST Calculator

How to calculate GST

Adding GST is straightforward: take the price without tax and put the tax on top. GST amount = Price × Rate ÷ 100, and the total is Price + GST. If a product costs ₹1,000 before tax and the rate is 18%, the GST is ₹180 and the final total is ₹1,180.

Removing GST works backwards. When a price shown to you already includes the tax — which is almost always the case at shops and in invoices — divide to find the price before tax: Price before GST = Inclusive price × 100 ÷ (100 + Rate). From ₹1,180 that includes 18%, the pre-tax price is ₹1,000 and the GST is ₹180.

Choose "Add GST" when your number is the pre-tax price and "Remove GST" when it already includes tax. The common mistake is subtracting the rate directly from an inclusive price: 18% of ₹1,180 is ₹212.40, which leaves ₹967.60 — not the correct ₹1,000. Always divide by (100 + rate) instead.

Current GST rates in India

Since 22 September 2025 the main GST slabs are 0%, 5%, 18% and 40%. The older 12% and 28% slabs were largely removed, so the rates you meet day to day mostly fall into four buckets:

• 0% — unbranded essential food items and a few basic goods.
• 5% — many daily essentials, packaged staples and some services.
• 18% — most services, electronics and many common goods; this is the rate you will encounter most often.
• 40% — a small group of luxury and sin goods, such as aerated drinks and high-end vehicles.

Special rates still exist outside these slabs — for example 3% on gold. This calculator accepts any rate from 0 to 100%, so you can enter those too, or work out an older invoice that used 12% or 28%.

CGST, SGST and IGST explained

GST is divided between the state and central governments depending on where the buyer is. When seller and buyer are in the same state, the tax is split in half: CGST (central GST) and SGST (state GST), each equal to half the total GST.

When the buyer is in a different state, the sale is inter-state and the full amount is collected as IGST. So ₹100 of GST on a same-state sale is ₹50 CGST + ₹50 SGST, while the same ₹100 on a sale to another state is ₹100 IGST.

Common GST mistakes to avoid

• Subtracting the GST rate directly from a price that already includes GST instead of dividing by (100 + rate) — taking 18% off ₹1,180 leaves ₹967.60, not the true pre-tax ₹1,000.
• Using the wrong rate for the item — always check the HSN/SAC code for a new product or service before you invoice.
• Forgetting that a sale to a buyer in another state is inter-state, so it carries IGST — not CGST and SGST.
• Rounding the GST amount and the total separately, so the two numbers on the invoice no longer add up.
• Not keeping the breakup handy — invoices in India must show the taxable value, the rate and the CGST, SGST and IGST figures.