GST Calculator
Add or remove GST and see the CGST, SGST or IGST split for any amount.
How to use the GST calculator
Choose whether your amount is before GST or already includes GST. Enter the amount and the GST rate, or tap one of the rate buttons. Then choose whether the sale is within one state or between two states. The result updates as you type and shows the taxable value, each tax component and the final total.
Adding GST to a price
When you have a price before tax, multiply it by the rate and divide by 100 to get the GST, then add it to the price. At 18%, a ₹10,000 service attracts ₹1,800 GST, and the invoice total is ₹11,800.
Removing GST from a price
When a price already includes GST, many people subtract the rate directly, which gives the wrong answer. The correct method is to divide the total by (1 + rate ÷ 100). For ₹11,800 at 18%, the value before tax is 11,800 ÷ 1.18 = ₹10,000, and the GST inside it is ₹1,800. If you had simply taken 18% of ₹11,800, you would get ₹2,124, which is too much. This tool always uses the correct reverse calculation.
CGST, SGST and IGST
For a supply inside one state, GST is divided equally between the Centre and the state. An 18% rate becomes 9% CGST and 9% SGST. In Union Territories without their own legislature, UTGST is charged instead of SGST. For a supply from one state to another, the full rate is charged as IGST. The total tax is the same either way; only the split on the invoice changes. Our guide on how GST works on a bill explains this in more detail.
Which rate applies?
GST rates depend on the goods or services and are revised by the GST Council from time to time. A major rate rationalisation in 2025 moved most items into the 5% and 18% slabs, with 40% for a small group of luxury and sin goods, while some items carry special rates such as 3% for gold. Because rates change, check the current rate for your item on the official CBIC GST website or with your tax adviser, and type it into the rate box. The calculator accepts any rate, including decimals.
Who uses this tool
Shopkeepers use it to quote prices inclusive of tax, freelancers to prepare invoices, and buyers to check how much tax is included in a bill. Accounts students use it to practise invoice problems.
This calculator is for general guidance and is not tax advice.
Frequently asked questions
How do I calculate GST from a total that already includes tax?
Choose “Remove GST”, enter the total and the rate. The tool divides the total by (1 + rate ÷ 100) to find the value before tax, then shows the GST amount.
Why is GST split into CGST and SGST?
For sales within one state, the tax is shared equally between the central and state governments, so the invoice shows two equal halves. Sales between states show a single IGST line.
Can I use rates like 0.25% or 1.5%?
Yes. Type any rate, including decimals, into the GST rate box.