GST Calculator

Add GST to a price, or work backwards from a GST-inclusive amount to the base value and tax.

This calculates the arithmetic only. Which rate applies to your goods or services, and whether the supply is intra-state or inter-state, is a matter for your accountant — this is not tax advice.

What is your amount?

GST will be added on top of the amount you enter.

Amount before GST

₹

GST rate

Or enter a rate

Total including GST

₹11,800.00

₹10,000.00 base + ₹1,800.00 GST at 18%

Base amountTaxable value: ₹10,000.00
GST at 18%: ₹1,800.00
Total: ₹11,800.00

Within a state

CGST 9%: ₹900.00
SGST 9%: ₹900.00

Between states

IGST 18%: ₹1,800.00

How this is calculated

GST = ₹10,000.00 × 18 ÷ 100

What this tool does

GST calculations run in two directions and people mix them up constantly. Adding GST to a net amount is simple multiplication. Extracting GST from a total that already includes it is not — taking 18% off a GST-inclusive ₹1,180 gives ₹967.60, which is wrong. The correct base is ₹1,000, because the ₹180 of tax was calculated on the base, not on the total.

This handles both, and shows the CGST/SGST and IGST splits side by side. Which split applies depends on whether the supply crosses a state border — that is a fact about the transaction, not something a calculator can infer, so both are shown.

When you might need it

Quoting a client: You know what you want to earn; you need the figure to put on the invoice with tax added.
A supplier quoted an inclusive price: You need the base value to record, and the tax portion to claim as input credit.
Checking an invoice you received: Confirm the tax line matches the rate and the base before it goes into the books.
Pricing a product: Work backwards from the shelf price a customer will accept to the revenue you actually keep.

Common workplace uses

Preparing a quotation: Show the client a net figure, a tax line and a total that add up correctly.
Reconciling a purchase invoice: Split an inclusive total into base and tax so each posts to the right ledger.
Setting a retail price: Decide the inclusive price first, then check what net revenue is left after tax.
Checking a vendor’s arithmetic: A quick confirmation that the tax charged matches the rate claimed.

How to use it

Say what your amount is
Excluding GST means tax will be added on top. Including GST means the figure already contains tax and will be worked backwards.
Enter the amount
The rupee value you are starting from.
Pick a rate
Tap 5, 12, 18 or 28 for the common slabs, or type any other rate in the field below.
Read the split
The total, the base and the tax appear immediately, with CGST/SGST shown for supply within a state and IGST for supply between states.

Practical tips

Never subtract the rate to remove GST: Taking 18% off an inclusive ₹1,180 gives ₹967.60. The right answer is ₹1,000, found by dividing by 1.18. The Including GST mode does this for you.
CGST and SGST are each half the rate: An 18% intra-state supply is 9% CGST plus 9% SGST — not 18% each. The total tax is the same either way; only the split differs.
Use IGST when the supply crosses a state line: Inter-state supply carries the whole rate as IGST. Which applies depends on place of supply rules, so check the transaction rather than guessing.
Rounding differences are normal: Invoicing systems round each line, then the total. A rupee or two of difference against this calculator is usually rounding, not error.
The rate depends on the goods or service: This tool does the arithmetic for whatever rate you give it. It cannot tell you which rate is correct for what you sell.

Common questions

How do I remove GST from an inclusive amount?

Switch to Including GST and enter the total. The base is the total divided by (1 + rate ÷ 100), and the tax is the difference. Subtracting the percentage directly gives the wrong answer.

What is the difference between CGST, SGST and IGST?

For supply within a single state the tax is split equally into CGST (central) and SGST (state). For supply between states the whole amount is charged as IGST. The total tax is identical; only the allocation differs.

Which GST rate applies to my product?

This calculator cannot tell you. Rates depend on classification and change with policy. Check the current schedule or ask your accountant — the tool handles the arithmetic once you know the rate.

Is this tax advice?

No. It performs a calculation you specify. It does not know your registration status, place of supply, input credit position or filing obligations. For anything that affects a return, use a qualified professional.

Can I use a rate that is not in the list?

Yes. The preset buttons cover the common slabs, but the rate field accepts any value, including cess percentages you want to model separately.

Does it handle rounding the way an invoice would?

It shows unrounded figures to two decimal places. Accounting systems apply their own rounding at line and invoice level, so small differences against a real invoice are expected.