GST Calculator
Calculate GST instantly with a clear breakdown of tax and final amount — accurate CGST, SGST and IGST splits, and the correct reverse formula for taking GST back out of an inclusive price.
GST will be added on top of this figure.
Presets, not tax advice — the slab that applies depends on the HSN/SAC classification of what you are selling.
Same state — 18% splits into CGST 9% + SGST 9%.
GST Breakdown
Add GSTIntra-stateGST 18%| Taxable Amount | ₹0 |
|---|---|
| CGST @ 9% | ₹0 |
| SGST @ 9% | ₹0 |
| Total GST | ₹0 |
Enter an amount to calculate GST.
Need an invoice?
Carry this calculation straight into the Invoice Generator — the amount, GST rate, quantity, discount and CGST/SGST split all arrive filled in.
The formula being used
GST = Taxable Amount × Rate ÷ 100Total = Taxable Amount + GSTTaxable = Inclusive × 100 ÷ (100 + Rate)GST = Inclusive − TaxableRemoving GST divides rather than subtracts. Taking 18% off ₹11,800 gives ₹9,676, which is wrong — the tax was charged on ₹10,000, not on the inclusive figure.
What is GST?
GST — Goods and Services Tax — is India's single indirect tax on the supply of goods and services. It replaced a stack of older levies (VAT, service tax, excise and several cesses) with one tax charged at each stage of the supply chain, where a registered business can claim back the GST it paid on its own inputs. The person at the end of that chain is the one who actually bears it.
In practice that means two numbers matter on any bill: the taxable value of what is being sold, and the GST charged on top of it. This calculator works out either one from the other, which is the whole job — going forwards when you are quoting a price, and backwards when someone hands you a price that already includes the tax.
How to calculate GST
Adding GST to a price
When the figure you have is the price before tax:
GST = Taxable Amount × GST Rate ÷ 100Total = Taxable Amount + GST₹10,000 at 18% → GST is 10,000 × 18 ÷ 100 = ₹1,800, so the total is ₹11,800.
Removing GST from a price
When the figure you have already includes the tax:
Taxable Amount = Inclusive × 100 ÷ (100 + Rate)GST = Inclusive − Taxable Amount₹11,800 including 18% → 11,800 × 100 ÷ 118 = ₹10,000 taxable, so the GST inside it is ₹1,800.
The mistake worth avoiding: subtracting instead of dividing
Taking 18% off a GST-inclusive ₹11,800 gives ₹9,676 — and it is wrong. The 18% was never charged on ₹11,800; it was charged on ₹10,000, and ₹1,800 of tax is what turned ₹10,000 into ₹11,800. Reversing a percentage always means dividing by (100 + rate), never subtracting the rate. On a large invoice that difference runs into thousands of rupees, and it is the error that shows up most often in hand-made spreadsheets.
CGST, SGST and IGST
The GST rate is the same either way. What changes is how the tax is split between governments, and that depends on whether the supply crosses a state border.
CGST
The central government's half of the GST on a supply made within a single state. It is charged at half the total rate, so an 18% supply carries 9% CGST.
SGST
The state government's half of the same tax, at the same half rate. CGST and SGST always appear together and always add up to the full GST rate. Union territories without a legislature use UTGST in its place.
IGST
One combined levy charged at the full rate, used when the place of supply is in a different state or union territory from the supplier, and on imports. It is collected centrally and then apportioned, which is why the invoice shows a single line rather than a split.
The same ₹10,000 at 18%, both ways
| Supply | Tax lines on the invoice | Total GST |
|---|---|---|
| Within one state | CGST @ 9% = ₹900 · SGST @ 9% = ₹900 | ₹1,800 |
| Across states | IGST @ 18% = ₹1,800 | ₹1,800 |
Note: this is a calculator, not tax advice. Which rate applies to a particular good or service depends on its HSN/SAC classification and the notifications in force at the time, and the place-of-supply rules that decide between CGST+SGST and IGST have their own exceptions. Confirm the treatment of your own supply with the official GST portal or a qualified practitioner before relying on a figure.
How to use this calculator
- 1
Choose Add or Remove GST
Pick Add GST if the amount you have is before tax, or Remove GST if it already includes tax and you need the taxable value underneath it.
- 2
Enter the amount
Type the figure into the amount field. The breakdown recalculates on every keystroke — there is no calculate button to press.
- 3
Pick the GST rate
Tap one of the 0%, 3%, 5%, 12%, 18% or 28% presets, or choose Custom and type any rate up to 100%.
- 4
Set the supply type
Intra-state splits the tax into CGST and SGST at half the rate each. Inter-state charges the whole rate as a single IGST line.
- 5
Add quantity or a discount
Set a quantity to multiply before tax, and open Discount to take a percentage or a fixed amount off the taxable value first.
- 6
Copy the result or raise an invoice
Copy the breakdown as text, share a link that reopens the same calculation, or send it to the Invoice Generator to turn it into a GST invoice.
Frequently asked questions
Multiply the taxable amount by the GST rate and divide by 100. On ₹10,000 at 18%, that is 10,000 × 18 ÷ 100 = ₹1,800 of GST, giving ₹11,800 in total. Enter the amount above, pick the rate, and the breakdown updates as you type.
More business tools
Free, no account, and the same three of them are the same editor in different modes — an invoice, a quotation and a receipt are one document with a different heading.