GST Calculator

What this tool does

The GST Calculator adds GST to a net price or extracts it from a GST-inclusive amount. It shows the CGST and SGST split for supplies within a state or IGST for inter-state supplies, supports quantities and custom rates, and produces an invoice-style breakdown.

Goods and Services Tax is charged on most supplies in India. Since the rate rationalisation that took effect on 22 September 2025, most goods and services fall into a 5% merit slab or an 18% standard slab, with a 40% rate for luxury and sin goods; special rates such as 3% on gold and 0.25% on rough diamonds continue, and some items are nil-rated. For a sale within one state the tax is split equally into CGST and SGST (or UTGST); for a sale between states the full amount is IGST.

In Add mode the tool computes GST = taxable value × rate ÷ 100. In Remove mode it extracts tax from an inclusive price with taxable value = price ÷ (1 + rate/100), which is the correct reverse calculation; subtracting the rate from the inclusive price gives the wrong answer. Results appear instantly and nothing leaves your browser.

How to use GST Calculator

1. Choose Add GST if your price excludes tax, or Remove GST if it already includes tax.
2. Enter the amount per unit and the quantity.
3. Pick the GST rate from the presets, or choose Custom rate and type it in.
4. Select whether the supply is within the same state or between states.
5. Read the taxable value, total GST and the CGST/SGST or IGST split.
6. Download the invoice breakdown as CSV if you need it for records.

Tips for better results

• Confirm the rate for your exact HSN (goods) or SAC (services) code; rates are set per item, not per business.
• On an 18% inclusive price, the GST portion is 15.25% of the amount, not 18%.
• Place of supply decides CGST + SGST versus IGST, not the location of the buyer’s head office.
• Registered businesses can usually claim input tax credit on GST paid on purchases used for business.

Common use cases

• Preparing a quote or invoice with the correct tax split.
• Finding the pre-tax price of an item bought at a GST-inclusive price.
• Checking the tax charged on a restaurant, hotel or service bill.
• Recalculating prices after the September 2025 rate changes.

Common mistakes to avoid

• Calculating reverse GST as price × (1 − rate); always divide by (1 + rate).
• Charging CGST and SGST on an inter-state sale, which should carry IGST.
• Using an old 12% or 28% rate for items moved into the new slabs in 2025.