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To add GST to a price, multiply it by the rate: GST = price × rate ÷ 100. A ₹10,000 item at 18% carries ₹1,800 of GST, so the bill is ₹11,800. To find GST inside an inclusive price, use GST = price × rate ÷ (100 + rate): an ₹11,800 bill at 18% contains ₹1,800 of GST on a ₹10,000 base. Within one state the tax is split equally into CGST and SGST; between states it is charged as a single IGST.
The guide at a glance
- To add GST, multiply the base price by the rate: ₹10,000 at 18% carries ₹1,800 of GST.
- To extract GST from an inclusive price, use price × rate ÷ (100 + rate), not a straight percentage of the price.
- Within a state, GST splits equally into CGST and SGST; between states it is charged as a single IGST.
- Since 22 September 2025, most items fall in the 5% or 18% slabs, with 40% for a short list of goods.
GST exclusive: adding tax to a price
When a price is quoted "plus GST", the base is known and GST is added on top.
- Formula: GST = base × rate ÷ 100; total = base + GST.
- Example at 18%: base ₹10,000 → GST ₹1,800 → total ₹11,800.
- Example at 5%: base ₹2,000 → GST ₹100 → total ₹2,100.
A quick check: at 18%, the total is always 1.18 times the base; at 5%, 1.05 times.
GST inclusive: taking tax out of a price
Retail prices and MRPs already include GST. To find the tax inside them, divide rather than subtract a percentage.
- Formula: base = price × 100 ÷ (100 + rate); GST = price − base.
- Example: a ₹1,000 inclusive price at 18% has a base of about ₹847.46 and GST of about ₹152.54.
The common mistake is taking 18% of ₹1,000 (₹180). That overstates the tax, because the 18% applies to the base, not to the tax-inclusive price. Our GST calculator does both directions.
Shortcut fractions
For an inclusive price, the GST share is rate ÷ (100 + rate). At 18%, that is 18/118, or about 15.25% of the price; at 5%, 5/105, or about 4.76%; at 40%, 40/140, or about 28.6%. So a ₹2,360 inclusive bill at 18% contains ₹360 of GST on a ₹2,000 base. If a discount is shown on the invoice before tax, GST is charged on the discounted value, not on the original list price.
CGST + SGST vs IGST
Which tax applies depends on the place of supply, not on the product.
- Intra-state supply (seller and place of supply in the same state): the rate is split half and half into Central GST and State GST. On the ₹10,000 example at 18%, that is CGST ₹900 + SGST ₹900. In union territories without a legislature, UTGST replaces SGST.
- Inter-state supply (seller in one state, buyer in another) and imports: a single Integrated GST at the full rate — IGST ₹1,800 on the same example.
The total tax is the same either way. The split decides which government receives it and how a registered business uses input tax credit.
GST rate slabs
After the rate rationalisation that took effect on 22 September 2025, most goods and services fall into two main slabs: 5% and 18%. A higher 40% rate applies to a short list of luxury and "sin" goods, many essentials are exempt or nil-rated, and a few items have special low rates, such as 3% on gold and jewellery. Rates for individual goods and services are set by notification and can change after GST Council meetings, so always check the current rate for a specific item in the official CBIC rate schedule or on your invoice's HSN or SAC code rather than relying on a list.
Worked example: a small business invoice
A Pune-based designer bills a Pune client ₹50,000 for services at 18%.
- Taxable value: ₹50,000
- CGST at 9%: ₹4,500 · SGST at 9%: ₹4,500
- Invoice total: ₹59,000
The same invoice to a client in Bengaluru would show IGST at 18% — ₹9,000 — and the same ₹59,000 total. If the designer paid ₹3,600 of GST on software and equipment used for the business, that input tax credit can be offset, so only the balance is paid to the government (subject to the credit rules).
Who has to charge GST?
- Businesses must register once their turnover crosses the threshold — generally ₹40 lakh for goods and ₹20 lakh for services, with lower limits in some special-category states.
- Small businesses can opt for the composition scheme, paying a low flat rate on turnover but without charging GST to customers or claiming input credit.
- Registered businesses must issue GST invoices showing the rate, the tax split and the place of supply.
GST is separate from income tax. A freelancer may charge GST to clients and also face TDS on payments received — see the TDS calculator. For pricing decisions, the Profit Margin calculator helps you set a price before tax is added.
Work out tax on any amount, inclusive or exclusive, intra- or inter-state, with the GST calculator.
Frequently asked questions
How do I calculate GST from a total amount?
Divide by (100 + rate) and multiply by the rate. For an ₹11,800 bill at 18%, GST is 11,800 × 18 ÷ 118 = ₹1,800, and the base price is ₹10,000. Taking 18% of the total would overstate the tax, because the rate applies to the base, not to the tax-inclusive price.
What is the difference between CGST, SGST and IGST?
For a sale within one state, GST is split equally into Central GST and State GST — on ₹10,000 at 18%, ₹900 each. For a sale from one state to another, or an import, a single Integrated GST of ₹1,800 applies. The total tax is the same; the split decides which government receives it.
What are the GST slabs in India now?
Since the rate changes effective 22 September 2025, most goods and services fall in two main slabs, 5% and 18%. A 40% rate applies to a short list of luxury and sin goods, many essentials are exempt, and a few items such as gold have special low rates. Rates for specific items change by notification, so check the CBIC schedule.
Written and fact-checked by the CoinCalc Team against official sources. Last updated . Read how we calculate and review. Educational content, not investment or tax advice.
- GST goods and services rates — Central Board of Indirect Taxes and Customs (CBIC)
- GST Acts — CGST, IGST, UTGST and compensation cess — Central Board of Indirect Taxes and Customs (CBIC)
