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GST calculator — add or remove GST.

Add GST to a price, or work backwards from a GST-inclusive amount. See the taxable value, CGST and SGST or IGST, and the invoice total, then download the working as a PDF.

What do you want to work out?
Calculation
Amount before GST (₹)
GST rate
Where is the supply?
Invoice total
₹11,800.00
GST at 18%: ₹1,800.00
Working
Taxable value₹10,000.00
CGST (9%)₹900.00
SGST (9%)₹900.00
Total GST₹1,800.00
Invoice value₹11,800.00
Formula: GST = amount × 18 ÷ 100, and the invoice total is the amount plus GST.
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One workspace for every GST return.

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Need an invoice to go with the figures? Use the GST tax invoice format, or check a late return with the GST late fee calculator.

How the GST calculator works

To add GST, multiply the price before tax by the rate and divide by 100. The result is the tax, and the price plus the tax is the invoice value. At 18%, a price of ₹10,000 carries ₹1,800 of GST and an invoice value of ₹11,800.

To remove GST from an amount that already includes it, divide by one plus the rate. At 18%, ₹11,800 divided by 1.18 gives ₹10,000, so the GST in it is ₹1,800. Subtracting 18% of ₹11,800 gives ₹9,676, which is wrong, because the 18% was charged on the smaller figure.

For a supply within a state, the tax is split equally between the central GST and the state GST. For a supply between states, the full amount is integrated GST. The total tax is the same either way. The rate itself depends on the item, so the calculator takes the rate as an input and does not classify goods or services.

Worked example: reverse GST on a bill of ₹5,900

A shop bill shows a total of ₹5,900 including 18% GST for a supply within the state. How much is the taxable value and how much is the GST?

Inputs
Amount including GST₹5,900
Rate18%
SupplyWithin the state
Output
Taxable value₹5,000.00
CGST at 9%₹450.00
SGST at 9%₹450.00
Total GST₹900.00
₹5,900 divided by 1.18 is ₹5,000. The GST is ₹5,900 minus ₹5,000, which is ₹900, split equally into ₹450 of CGST and ₹450 of SGST.

Common mistakes

Subtracting the percentage instead of dividing
Taking 18% off an inclusive amount understates the tax. Always divide by one plus the rate to recover the taxable value.
Using the old rate on a new invoice
Most goods and services moved to 5% or 18% from 22 September 2025, and the 12% and 28% slabs were retired for most items. Check the rate that applied on the date of supply for the item you are billing.
Mixing CGST and SGST with IGST on one line
A single supply is either within a state or between states. Showing both kinds of tax on one line is a common invoice error.
Rounding each line and then the total
Rounding at different stages can leave a rupee of difference between the invoice and the return. Decide the rounding rule once and apply it consistently.
Treating the calculator as classification
The item decides the rate. If the classification is uncertain, confirm the HSN or SAC and the notified rate before issuing the invoice.

Frequently asked questions

How do I calculate GST on a price?+
Multiply the price before tax by the GST rate and divide by 100. Add the result to the price to get the invoice value. For example, 18% GST on ₹10,000 is ₹1,800, so the invoice value is ₹11,800.
How do I remove GST from an inclusive amount?+
Divide the amount by one plus the rate. For an amount of ₹11,800 at 18%, divide by 1.18 to get a taxable value of ₹10,000. The difference, ₹1,800, is the GST.
What are the GST rates in India in 2026?+
Since 22 September 2025, most goods and services are taxed at 5% or 18%, with 40% for demerit and luxury items, nil for exempt items, and special rates of 3% for gold and 0.25% for rough diamonds. The 12% and 28% slabs were retired for most items. Check the notification for your specific item.
What is the difference between CGST, SGST and IGST?+
CGST goes to the central government and SGST to the state government, each at half the rate, on a supply within a state. IGST is charged on a supply between states, at the full rate, and is shared between the centre and the destination state.
Is this calculator the same as reverse GST?+
Yes. Choose "Remove GST" to work backwards from an amount that already includes GST to the price before tax.

Authoritative sources

CGST Act, 2017 and GST rate notifications, CBIC — Rate structure checked 9 October 2026 from public summaries of the 22 September 2025 rationalisation. The rate for an item is as notified; confirm on the CBIC rate page before invoicing.
Always confirm against the latest version of the source. Regulations evolve and amendments are common.
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GST late fee calculator →GST interest calculator →GST refund calculator →GST tax invoice format →
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Last reviewed: 2026-10-09 · For informational purposes only — not professional advice.