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Free tool · Updated 2026

GST Calculator

Add GST to a base price or strip GST out of a total, at 5%, 12%, 18% or 28%. See the CGST and SGST split for local sales, or IGST for inter-state sales, calculated instantly.

Your amount

Add or remove GST, with the tax split.

₹
Total (incl. GST)
₹0
base plus GST
Base amount₹0
Total GST₹0
CGST (half)₹0
SGST (half)₹0
Total amount₹0
Rates shown are the common GST slabs. The exact rate depends on your product's HSN/SAC code. Estimate only.

How the GST calculation works

GST is charged as a percentage of the value of goods or services. In add-GST mode, the calculator takes your base amount and adds the tax on top, so ₹10,000 at 18% becomes ₹10,000 base plus ₹1,800 GST, a total of ₹11,800. In remove-GST mode, it works backwards from a GST-inclusive price: it divides the total by one plus the rate to find the base, then shows the GST portion. This reverse calculation is what you need when a supplier quotes an all-inclusive price and you want to know the tax inside it.

CGST, SGST and IGST, explained

Which taxes apply depends on where the buyer and seller are. For a sale within the same state (intra-state), GST is split equally between the centre and the state, so an 18% rate becomes 9% CGST plus 9% SGST. For a sale between different states (inter-state), the entire tax is charged as IGST. The total tax is the same either way; only the split differs. This calculator shows the correct breakup as soon as you choose the sale type.

Getting the rate right

The common GST slabs are 5%, 12%, 18% and 28%, but the rate that applies to you depends on the HSN code (for goods) or SAC code (for services) of what you sell. Using the wrong rate on your invoices can lead to short payment, interest, and mismatches that trigger notices. If you are unsure which slab your product falls in, it is worth confirming with a professional before you invoice.

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Frequently asked

How do I add GST to an amount?
Multiply the base amount by the GST rate. For example, at 18% on ₹1,000 the GST is ₹180 and the total is ₹1,180. This calculator does it instantly and also splits the tax into CGST and SGST for within-state sales, or IGST for inter-state sales.
How do I remove GST from a total (reverse GST)?
When a price already includes GST, the base is the total divided by (1 plus the rate). At 18%, a ₹1,180 GST-inclusive price has a base of ₹1,000 and GST of ₹180. Switch this calculator to remove-GST mode to do it automatically.
What is the difference between CGST, SGST and IGST?
For a sale within the same state, GST is split equally into CGST (central) and SGST (state), so 18% becomes 9% plus 9%. For a sale between states, the whole amount is charged as IGST. This tool shows the correct split when you pick intra-state or inter-state.
Which GST rate applies to my product?
The common GST slabs are 5%, 12%, 18% and 28%, with some goods and services at 0% or special rates. The rate depends on the HSN or SAC code of your product or service. If you are unsure, a CA can confirm the correct classification.