GST calculator

How GST is calculated

GST is charged on the taxable value: the price of the goods or services after any discount shown on the invoice. The formulas are simple:

• Adding GST: GST = taxable value × rate ÷ 100. Price with GST = taxable value + GST.
• Removing GST: taxable value = inclusive price ÷ (1 + rate ÷ 100). GST = inclusive price − taxable value.

Amounts are rounded to the paisa. When removing GST, this calculator works out the taxable value first and treats the rest of the price as tax, so the two always add back to exactly the price you typed. That is the same method InDhanPay Books uses for MRP-style prices on an invoice.

CGST, SGST and IGST

India has one GST, collected by both the Centre and the states. For a sale inside a state, half the tax is central GST (CGST) and half is state GST (SGST), so 18% becomes 9% + 9%. In a union territory without its own legislature, such as Chandigarh or Ladakh, UTGST takes the place of SGST. For a sale from one state to another, the whole tax is integrated GST (IGST), collected by the Centre and passed on to the state where the goods or services are consumed. The buyer can claim input tax credit for any of them when they are registered and the invoice is correct.

Which one applies depends on the place of supply, which for most goods is where they are delivered. On a GST invoice, the place of supply is printed with the state name and code. Our free GST invoice generator picks the right split for you from the two states, and the GSTIN checker reads the state code from a GSTIN.

The GST rates in force

From 22 September 2025 GST moved to two main rates, 5% for essentials and 18% as the standard rate, plus 40% for luxury and sin goods. Gold, silver and jewellery stay at 3% and rough precious stones at 0.25%. Many items such as fresh produce, milk and most healthcare services are exempt. The 12% and 28% slabs are listed in the calculator as old rates so you can still check a bill from before the change.

The rate for a product depends on its HSN code (SAC for services), not on what you call it. When in doubt, check the rate notified for your HSN code before you bill.

Worked examples

• ₹2,500 of goods at 5%, same state: CGST ₹62.50 + SGST ₹62.50, total ₹2,625.
• ₹10,000 of services at 18%, to another state: IGST ₹1,800, total ₹11,800.
• A ₹590 inclusive price at 18%: taxable value ₹500, GST ₹90.
• ₹1,00,000 of gold jewellery at 3%, same state: CGST ₹1,500 + SGST ₹1,500, total ₹1,03,000.

Billing every day? InDhanPay Books does this maths on every line of every invoice, prints the per-rate GST summary, and adds it all up for your GSTR-1 and GSTR-3B. It suits shops, restaurants and service businesses alike.