How do I calculate 18% GST on an amount?

Enter the amount, select 18% as the GST rate, and choose "Excluding GST" if your amount doesn't already include tax. The calculator shows the GST amount and the total instantly — no manual math needed.

What is a reverse GST calculator and how do I use it?

A reverse GST calculator extracts the tax portion from a total (GST-inclusive) amount instead of adding it on top. Enter the total amount, select the applicable GST rate, and choose "Including GST" — the calculator works backward to show the taxable value and the GST amount within that total.

What's the difference between GST inclusive and GST exclusive amounts?

A GST-exclusive amount is the price before tax — GST is added on top to arrive at the total. A GST-inclusive amount is the final price a customer pays, with GST already baked in. Use the "Amount entered is" toggle to tell the calculator which one you have.

What's the difference between CGST/SGST and IGST?

CGST and SGST apply to intra-state supply — the total GST is split equally between central and state tax (e.g. 9% + 9% for an 18% rate). IGST applies to inter-state supply and is charged as a single line at the full GST rate. Select the supply type to see the correct split.

How do I add GST to an invoice amount?

Enter the invoice amount (excluding GST), pick the GST rate that applies to your goods or service, and select the supply type. The calculator shows the GST amount to add and the final invoice total, broken down into CGST/SGST or IGST.

Is this GST calculator free to use, and do I need to log in?

Yes — this GST calculator is completely free and requires no sign-up or login. It runs entirely in your browser.

Can small businesses use this GST calculator for invoicing?

Yes. It's built for freelancers, small businesses, and agencies that need to quote or invoice with GST — enter the amount and rate, and it handles the CGST/SGST or IGST split without needing accounting software.

How do I find the amount after GST on a base price of ₹10,000?

Enter ₹10,000, select 18% as the GST rate, and choose "Excluding GST." The amount after GST — the total including tax — shows as ₹11,800, with a ₹1,800 GST breakup into CGST/SGST or IGST depending on supply type.

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GST Calculator

Free online GST calculator to add or remove GST from any amount and see the CGST/SGST or IGST breakup instantly. No login required.

Amount (₹)

GST rate

Supply type

Amount entered is

Taxable amount₹1,000

CGST (9%)₹90

SGST (9%)₹90

Total amount₹1,180

How this tool works

This GST calculator works both ways: enter a GST-exclusive amount to add GST on top, or enter a GST-inclusive (total) amount to run a reverse GST calculation and pull the tax back out. It supports all four GST slabs — 5%, 12%, 18%, and 28% — with 18% being the default rate most freelancers, small businesses, and service providers use for invoicing.

If you're a freelancer, consultant, or agency adding GST to an invoice amount, the calculator also splits the tax correctly based on where your client is registered: CGST + SGST for intra-state supply (equal halves of the GST rate), or IGST for inter-state supply (the full rate as one line item).

Every figure — taxable amount, GST amount, and the CGST/SGST or IGST breakup — updates instantly as you type, so you can check GST on an invoice amount before you send it.

How to calculate GST on an invoice

1Enter the amount. Type the invoice or transaction amount in rupees.
2Choose the GST rate. Select the applicable slab — 5%, 12%, 18%, or 28%.
3Select inclusive or exclusive. Choose "Excluding GST" to add tax on top, or "Including GST" to reverse-calculate the tax from a total amount.
4Select the supply type. Choose "Intra-state" for a CGST/SGST split, or "Inter-state" for IGST.
5Read the breakup. The taxable amount, GST amount (CGST/SGST or IGST), and total update instantly.

Frequently asked questions

Want to turn this into a GST-compliant invoice? See Dharayana plans

Need payment tracking and automatic reminders too? See the full GST Invoicing app.