How do I calculate GST on an amount?

Multiply the amount by the GST rate and divide by 100. For ₹5,000 at 18%, GST = 5,000 × 18 ÷ 100 = ₹900, so the total is ₹5,900.

How do I remove GST from an inclusive price?

Divide the amount by (100 + rate) and multiply by 100. For ₹5,900 including 18% GST: 5,900 × 100 ÷ 118 = ₹5,000. The GST is ₹900.

When is IGST charged instead of CGST and SGST?

IGST applies when the supplier and the place of supply are in different states, and on imports. Sales within the same state attract CGST plus SGST.

Can I use a GST rate that is not listed?

Yes. Choose “Custom” and type any rate, such as 0.25% or 1.5%.

Is this calculator suitable for filing returns?

It is meant for quick checks and quotations. For invoices and returns, follow the official GST rules and your accounting software.

GST Calculator – Add or Remove GST, CGST & SGST

How to use the GST Calculator

Choose Add GST if your amount is before tax, or Remove GST if the amount already includes GST.
Enter the amount.
Select the GST rate, or pick Custom to type any rate.
Choose whether the sale is within your state (CGST + SGST) or to another state (IGST) to see the correct split.

Formula

Add GST: GST = Amount × Rate ÷ 100

Remove GST: Net = Amount × 100 ÷ (100 + Rate)

For a sale within the same state, GST is split equally: CGST = SGST = GST ÷ 2.
For a sale to another state (or an import), the full amount is charged as IGST.

Worked example: Adding and removing 18% GST

Adding: a service priced at ₹10,000 + 18% GST → GST = ₹1,800, total = ₹11,800. Within the state this is ₹900 CGST + ₹900 SGST.

Removing: a bill of ₹11,800 that includes 18% GST → net value = 11,800 × 100 ÷ 118 = ₹10,000, and GST = ₹1,800.

A common mistake is to take 18% of ₹11,800 (₹2,124). That overstates the tax – always divide by 118 when GST is already included.

GST rates in India

After the GST rate rationalisation that took effect on 22 September 2025, most goods and services fall under two main slabs – 5% and 18% – with a special 40% rate for select luxury and sin goods. Special rates such as 3% (gold, silver) and 0.25% (rough diamonds) continue. You may still see 12% or 28% on older invoices, which is why those rates remain in the calculator.

Rates change from time to time and depend on the exact HSN or SAC code, so always confirm the rate for your product or service on the official CBIC website or with your tax advisor.

CGST, SGST and IGST explained

CGST goes to the Central Government and SGST (or UTGST in union territories) to the State Government when goods or services are sold within one state. IGST is charged on inter-state sales and is shared between the Centre and the destination state. The total tax is the same either way – only the split changes.