How is GST calculated on an amount?

To add GST: GST amount = (Original amount × GST rate) ÷ 100, and the total = original amount + GST. For example, ₹1,000 at 18% GST = ₹180 GST, so the total is ₹1,180.

How do I remove GST from a total (reverse GST)?

When a price already includes GST, the base amount = Total ÷ (1 + GST rate/100). For ₹1,180 at 18%, the base is ₹1,180 ÷ 1.18 = ₹1,000, and the GST included is ₹180. Use the "Remove GST" mode above to do this automatically.

What is the difference between CGST, SGST and IGST?

For sales within the same state, GST is split equally into CGST (central) and SGST (state) — e.g. 18% becomes 9% + 9%. For sales between states, the full rate is charged as IGST (integrated GST). Toggle the tax type above to see both.

What are the current GST slab rates in India?

After the GST 2.0 reform effective 22 September 2025, the main slabs are 0%, 5% and 18%, with a special 40% rate for luxury and sin goods. The earlier 12% and 28% slabs have been removed. Special rates of 0.25% (rough diamonds) and 3% (gold and precious metals) still apply. This calculator supports all of them plus a custom rate.

Can I calculate GST for multiple units or a quantity?

Yes. Enter a quantity and choose whether your amount is per unit or for all units. The calculator shows the taxable price, GST, and total both per unit and for the whole quantity, so the line total always matches.

Is this GST calculator free to use?

Yes — it is completely free, needs no login, and runs entirely in your browser. To generate GST invoices automatically, you can start a free trial of KhataBuddy.

Free Tool

GST Calculator

Add or remove GST on any amount — per unit or for all units — and split it into CGST, SGST or IGST. Instantly and free.

Your amount is before GST — we add the tax on top.

Amount (before GST)

₹

GST rate

Quantity

Sale type

Total amount with GST

₹1,180.00

Base price GST (18%)

Taxable price · before GST₹1,000.00

GST @ 18%₹180.00

CGST @ 9%

₹90.00

SGST @ 9%

₹90.00

Total amount₹1,180.00

Stop calculating by hand — KhataBuddy auto-applies GST to every invoice and files your returns.

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How to calculate GST

GST (Goods and Services Tax) is calculated as a percentage of the taxable value of a product or service. There are two common scenarios.

Adding GST (amount excludes tax)

GST amount = Original amount × (GST rate ÷ 100)
Total = Original amount + GST amount

Example: ₹1,000 at 18% → ₹180 GST → ₹1,180 total.

Removing GST (amount includes tax)

Base amount = Total ÷ (1 + GST rate ÷ 100)
GST included = Total − Base amount

Example: ₹1,180 at 18% → base ₹1,000 → ₹180 GST included.

Within a state, GST is split equally into CGST and SGST; across states the full rate is charged as IGST. The calculator above handles both, and works out per-unit and total prices for any quantity.

GST Calculator — FAQs

Common questions about calculating GST in India.

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