GST Calculator — Add or Remove GST at the 5%, 18% and 40% Rates

How to use the GST calculator

1. Type the Amount in rupees.
2. Under The amount, choose Excludes GST (add it) if the figure is a price before tax, or Includes GST (extract it) if tax is already inside it.
3. Pick the GST rate: 5% (merit rate), 18% (standard rate), 40% (special rate), 0% (exempt / nil) or Other rate. If you choose Other rate, type it in the box that appears.
4. Under Supply, choose Within a state (CGST + SGST) or Between states (IGST).
5. Read the result: the price before GST, the GST, its split, and the total including GST. When you remove GST, a note shows how far off you would be if you subtracted the percentage instead.

What it does and when to use it

GST is added on top of a price. A shop that sells something for ₹1,000 plus 18% GST bills ₹1,180. That part is easy. The harder job runs the other way: you have a total that already includes tax and you need to know how much of it is tax. That comes up all the time:

• Shopkeepers and freelancers setting a price that customers see as one tax-inclusive figure.
• Buyers checking how much GST is inside a bill, or how much input tax credit a business purchase carries.
• Accounts staff splitting a total into taxable value, CGST and SGST for an invoice or a return.
• Anyone comparing quotes, where one supplier quotes “plus GST” and another quotes “all inclusive”.

The calculator does both directions and splits the tax the way an Indian tax invoice shows it. Once you have the figures, you can put them on a bill with the Invoice Generator or a quote with the Proforma Invoice Generator.

GST rates from 22 September 2025

The 56th meeting of the GST Council, on 3 September 2025, recommended a simpler structure. The Press Information Bureau published the decisions, which took effect on 22 September 2025.

The older 12% and 28% slabs were folded into this structure. The Council’s FAQs add that tobacco items keep their earlier GST and compensation cess until the government notifies the change. Some goods also have their own special rates. For any rate that is not in the list, choose Other rate and type it in.

Which rate applies to a product is decided by its classification (the HSN code for goods or the SAC for services) and the rate notification for that code. Two products that look alike can fall under different headings, so check the notified rate before you print prices. This page does not list item-by-item rates.

How it works

Let A be the amount you type and r the GST rate in per cent.

Adding GST (the amount excludes tax):

• GST = A × r ÷ 100
• Total including GST = A + GST

Removing GST (the amount includes tax):

• Price before GST = A ÷ (1 + r ÷ 100)
• GST = price before GST × r ÷ 100

Splitting the tax:

• Within a state: CGST = SGST (or UTGST) = GST ÷ 2, each at half the rate. So 18% shows as 9% + 9%, and 5% as 2.5% + 2.5%.
• Between states: IGST = the full GST at the full rate.

The reason you must divide, not subtract, is that the tax was worked out on the smaller, pre-tax figure. Taking r% off the larger, tax-inclusive figure removes too little, so the base comes out too low. The calculator shows that gap whenever you remove GST. All the maths runs in your browser.

Worked examples

These figures come straight from the calculator.

1. Adding 18% within a state. A business charges ₹1,000 for a service taxed at 18%, to a customer in the same state. At that rate, the GST is ₹180, so the Total including GST: ₹1,180.00. The bill shows CGST (9%): ₹90.00 and SGST (9%): ₹90.00.

2. Taking 18% out of a total. A receipt says ₹1,180 including 18% GST. Dividing by 1.18 gives a price before GST of ₹1,000.00 and GST of ₹180.00. The calculator’s note says that subtracting 18% of ₹1,180 would understate the base by ₹32.40. On one bill that looks small. Across every line of a month’s sales it adds up.

3. A 5% supply between states. A seller in Gujarat ships goods worth ₹2,100 including 5% GST to a buyer in Rajasthan. The price before GST is ₹2,000.00, and the tax shows as one line: IGST (5%): ₹100.00.

4. The special 40% rate. For an item taxed at 40%, sold between states for ₹50,000 before tax, the GST is ₹20,000.00 and the Total including GST: ₹70,000.00. At this rate, getting the direction wrong is costly: subtracting 40% from ₹70,000 would give ₹42,000, not ₹50,000.

5. Checking an old invoice at 12%. An invoice from before 22 September 2025 shows ₹5,600 including 12% GST. With Other rate set to 12, the calculator gives Amount before GST: ₹5,000.00, with ₹300 each of CGST and SGST.

Limits and tips

• Rates change. The figures on this page were checked against the PIB release on the date shown. Rates for specific items are set by notification and can change after a Council meeting, so confirm the rate for your HSN or SAC code.
• No cess. The calculator handles one GST rate at a time. Where compensation cess still applies, add it separately.
• No input tax credit. The calculator does not work out what you can claim back on purchases or what you owe after credits. It works on one amount at a time.
• Rounding. Results show two decimal places. Invoices are often rounded per line or on the total, so small differences are normal.
• Composition scheme and exempt sellers. Some small businesses do not charge GST on their invoices at all. The calculator assumes GST is charged at the rate you choose.
• Discounts. If you offer a discount, apply it to the price before tax and then add GST. The Discount Calculator works out the sale price, and the Markup Calculator helps when you set a selling price from cost.

Pricing tips for sellers

• Decide whether your price list is “plus GST” or “inclusive of GST”, and say so clearly on quotes and labels. A business buyer that claims input tax credit will want to see the tax shown separately.
• If you want a round inclusive price such as ₹999, use Includes GST (extract it) to see the taxable value you must show on the invoice.
• When you sell to another state, the total does not change, but the invoice shows IGST instead of CGST and SGST. If you are unsure which applies to a sale, ask your accountant before you issue the invoice.