GST Calculator

What this calculator does

This calculator works out Goods and Services Tax on an amount. It can add GST to a net price or remove GST from a gross price, and it shows the net amount, the GST amount, the gross amount, and the CGST and SGST split. It is built around India’s GST slabs — 0%, 5%, 12%, 18% and 28% — with a Custom option for any other rate. Results recalculate instantly as you type, and every figure is computed locally in your browser.

Why you might need it

GST appears on almost every invoice, receipt and quotation, and people constantly need to move between tax-exclusive and tax-inclusive figures. A shopkeeper pricing an item knows the net cost and needs the gross shelf price. A buyer holding a final receipt wants to know how much of it was tax. An accountant reconciling a ledger needs the CGST and SGST components separately for filing. Doing this by hand is error-prone, especially across several rate slabs, so a calculator that handles both directions and the central-state split saves time and avoids mistakes.

How to use it

1. Choose a mode: “Add GST” if your amount is the net (pre-tax) price, or “Remove GST” if your amount already includes GST.
2. Enter the amount. The field label updates to “Net amount” or “Gross amount” so it is clear which figure you are entering.
3. Pick a GST rate from the slab buttons, or choose Custom and type a rate.
4. Optionally change the currency — it defaults to INR.
5. Read the results: net, GST and gross amounts, plus the CGST and SGST halves. Copy the GST amount with one click if you need it.

How it’s calculated

GST is a simple percentage. In Add mode the amount is the net value, so the gross is net × (1 + rate/100) and the GST is the difference between gross and net. In Remove mode the amount is the gross value, which already contains tax, so the net is recovered by dividing: net = gross ÷ (1 + rate/100). The GST is again the difference. Because removal divides rather than subtracts, you cannot simply take the rate percentage off an inclusive price — that is a common mistake the tool avoids for you.

The CGST and SGST values are each exactly half of the GST amount, which is how an intra-state supply is divided between the central and state governments.

Common pitfalls

The classic error is removing GST by subtracting the rate from the gross price — removing 18% from an inclusive ₹118 does not give ₹100, because the 18% was charged on ₹100, not ₹118. Always divide for the inclusive case. Another mistake is mixing up CGST/SGST with IGST: an inter-state supply is not split in half; it carries a single IGST charge equal to the full GST. Finally, make sure you have selected the rate slab that actually applies to the goods or service — the slab depends on the item.

Tips

When pricing items, work in Add mode so the shelf price already includes tax. When checking a receipt, use Remove mode to see the tax you paid. If a product attracts a compensation cess on top of GST, add it through the Custom rate field. For book-keeping, copy the GST figure and record the CGST and SGST halves separately. Switching the currency lets you reuse the same percentage logic for any other value-added tax that behaves the same way.