GST Calculator

When this applies

• You are raising an invoice and the CGST/SGST or IGST split must be shown as separate lines.
• A price is quoted GST-inclusive and you need the taxable value for your books.
• You are checking a supplier invoice where the tax looks wrong.
• You are quoting an inter-state customer and need the IGST figure before you commit.

Adding 18% GST to an intra-state supply

1. 1Base amount INR 10,000, rate 18%, supply within the state.
2. 2Taxable value = INR 10,000.
3. 3GST = 10,000 x 18 / 100 = INR 1,800.
4. 4CGST and SGST = 1,800 / 2 = INR 900 each.
5. 5Invoice total = 10,000 + 1,800 = INR 11,800.

The invoice shows INR 10,000 taxable, INR 900 CGST, INR 900 SGST and INR 11,800 payable.

What this calculator does

Add GST to a base amount, or take it back out of a GST-inclusive price, and see exactly how the tax splits. On a supply within one state it shows the CGST and SGST halves; on a supply between states it shows the single IGST line. The total tax is the same either way - only the split changes.

How this is calculated

For an exclusive amount the taxable value is the amount itself, and GST is taxable value x rate / 100. For an inclusive amount the taxable value is backed out first by dividing by (1 + rate / 100), and the GST is the difference between the inclusive amount and that taxable value. On an intra-state supply the GST is split equally into CGST and SGST; on an inter-state supply the same total is charged as IGST. The rate itself follows the HSN code for goods or the SAC code for services, which is why the calculator takes it as an input instead of guessing it.

The formula

Taxable = amount (exclusive) or amount ÷ (1 + rate/100) (inclusive) · GST = taxable × rate/100

Common mistakes to avoid

• Splitting CGST/SGST on an inter-state supply

  An inter-state supply carries IGST, not a CGST/SGST split. Raising an invoice with the wrong split is a common reason a customer cannot claim input credit.

• Treating an inclusive price as the taxable value

  Charging 18% on top of a price that already includes GST overstates the tax by about 18%. Back the taxable value out first.

• Applying the rate to the wrong base

  GST is a percentage of the taxable value, not of the invoice total. The two differ whenever the amount is inclusive.

• Assuming one rate fits the whole invoice

  A single invoice can carry several HSN/SAC classifications at different rates. Compute each line separately.

Frequently asked

What is the difference between CGST, SGST and IGST?

CGST and SGST are the central and state shares of GST on a supply within a single state, each charged at half the notified rate. IGST is charged instead, at the full rate, on a supply between states or across a border. The total tax is identical; only the split across the two heads differs.

How do I remove GST from an inclusive price?

Divide the inclusive amount by (1 + rate / 100) to get the taxable value, then subtract that from the inclusive amount to get the GST. At 18% on an inclusive INR 11,800, the taxable value is INR 10,000 and the GST is INR 1,800.

Which GST rate applies to my goods or service?

The rate follows the HSN code for goods or the SAC code for services, and is set by notification rather than by the calculator. Enter the rate that applies to your classification; if you are unsure of the classification, that is the question to settle first.

Does a discount reduce the GST?

A discount that is shown on the invoice and agreed before or at the time of supply reduces the taxable value, so the GST falls with it. A discount given later is treated differently and may need a credit note. Enter the value you are actually charging.

Can a composition dealer use this?

No. A composition dealer pays a flat rate on turnover and does not charge GST on individual invoices, so there is no CGST/SGST split to show. Use the composition tax calculator instead.

Is the amount I type sent anywhere?

No. Every calculation runs in your browser. Nothing you enter is transmitted to us or stored.