Use this free online GST calculator to quickly add GST to a base amount or remove GST from a GST-inclusive amount. It splits the tax into CGST and SGST for sales within a state, or shows it as IGST for sales between states, using the GST slabs in force since 22 September 2025.
How to Use the GST Calculator
Enter the "Amount (₹)" you want to calculate GST on.
Pick a GST slab (3%, 5%, 18% or 40%) or type any other rate in the field below it.
Choose the "GST Mode": "Add GST to amount" if your amount excludes tax, or "Remove GST from amount" if it's GST-inclusive.
Choose whether the sale is within your state or to another state, then click "Calculate GST" to see the base amount, the tax split and the total.
GST Formulas
There are only two formulas you need. Which one applies depends on whether the price you have already includes GST.
Adding GST (price excludes tax): GST = Base Price × Rate ÷ 100, and Total = Base Price + GST.
Removing GST (price includes tax): GST = Total × Rate ÷ (100 + Rate), and Base Price = Total − GST.
The second formula divides by (100 + Rate), not 100, because the GST is already inside the total. For example, at 18% you divide by 118.
Worked Examples
Adding GST to a base price of ₹10,000 at each slab:
GST Rate
GST Amount
CGST + SGST
Total
3%
₹300
₹150 + ₹150
₹10,300
5%
₹500
₹250 + ₹250
₹10,500
18%
₹1,800
₹900 + ₹900
₹11,800
40%
₹4,000
₹2,000 + ₹2,000
₹14,000
Removing GST from an MRP: a product sells for ₹1,180 including 18% GST. GST = 1,180 × 18 ÷ 118 = ₹180, so the base price is ₹1,000. Within the same state, that ₹180 is shown on the bill as ₹90 CGST and ₹90 SGST; if the seller is in another state, it is shown as ₹180 IGST.
GST Rate Slabs in India (from 22 September 2025)
Under the GST 2.0 reform approved by the GST Council in September 2025, the old 12% and 28% slabs were folded into a simpler structure. Most items now fall into one of these rates:
Rate
Typical items
0% (nil)
Fresh fruit and vegetables, fresh milk, eggs, UHT milk, paneer, roti and chapati, individual life and health insurance premiums
3%
Gold, silver and jewellery
5%
Everyday essentials such as soap, shampoo, toothpaste, hair oil, butter and ghee, most medicines, and tractors
18%
The standard rate for most goods and services, including air conditioners, larger TVs, small cars, two-wheelers up to 350cc, cement, and services like telecom and banking
40%
Luxury and sin goods such as pan masala, aerated and sugary drinks, large cars and motorcycles above 350cc
Rates for individual items are set by GST Council notifications and can change. Before issuing an invoice or filing a return, confirm the rate for your item's HSN or SAC code on the official CBIC GST portal.
CGST, SGST and IGST: Which One Applies?
When the seller and the place of supply are in the same state, the tax is split equally: half goes to the Centre as CGST and half to the state as SGST (or UTGST in a union territory without a legislature). At 18%, that is 9% CGST plus 9% SGST.
When goods or services move from one state to another, or are imported, the full rate is charged as a single IGST. The total tax is the same either way. Only the way it appears on the invoice, and which government receives it, is different.
Common GST Calculation Mistakes
Taking 18% of a price that already includes GST. On ₹1,180 that gives ₹212.40 instead of the correct ₹180, overstating the tax by ₹32.40. Use "Remove GST" mode for MRP and other tax-inclusive prices.
Charging CGST + SGST on a sale to a customer in another state. Inter-state sales must show IGST, or the buyer may be unable to claim input tax credit.
Still using the old 12% or 28% rates. Most items in those slabs moved to 5%, 18% or 40% on 22 September 2025, so check older price lists and billing software.
Rounding the tax on the invoice total when each line has a different rate. Calculate GST separately for each item at its own rate, then add them up.
Frequently Asked Questions
"Add GST" treats your entered amount as the base (tax-exclusive) price and calculates GST = base × rate / 100 on top of it. "Remove GST" treats your amount as tax-inclusive and works backward using base = total / (1 + rate/100) to extract the base price and GST portion.
The calculator splits the total GST amount equally in half — CGST and SGST each equal GST ÷ 2 — which reflects how intra-state GST is typically divided between central and state tax in India.
Yes. The MRP printed on packaged goods in India includes all taxes, so a shopkeeper cannot add GST on top of it. To see how much of an MRP is GST, enter the MRP and use "Remove GST" mode.
From 22 September 2025, most items taxed at 12% moved to 5%, most items at 28% moved to 18%, and a new 40% rate was introduced for luxury and sin goods. If you still need an old rate, for example to check an older invoice, type it into the custom rate field.
Registration is generally required once annual turnover crosses ₹40 lakh for suppliers of goods or ₹20 lakh for suppliers of services. The limits are lower in special category states, and some businesses, such as e-commerce sellers and inter-state suppliers, must register regardless of turnover.