About this gst calculator
Work GST out in either direction. Add it on top of a base price, or go the other way and find how much tax is already inside a GST-inclusive total — the reverse GST calculation you need when a price tag or MRP already includes tax. Enter the amount and the rate, commonly 5%, 12%, 18% or 28%, and you get the base price, the GST amount, the even CGST and SGST split used on an intra-state sale, and the total. The arithmetic runs in your browser, so an invoice figure you are checking is never sent anywhere. Useful for shopkeepers, freelancers and anyone checking whether a bill adds up.
How the gst calculator works
Adding GST: GST = base price × rate ÷ 100, and total = base price + GST. Reverse GST, extracting tax from an inclusive total: base price = total ÷ (1 + rate ÷ 100), and GST = total − base price. This is the one people get wrong by subtracting the rate from the total — taking 18% off ₹1,180 gives ₹967.60, not the correct ₹1,000, because the 18% was charged on the base price and not on the total. On an intra-state sale the GST amount is split evenly: CGST and SGST take half each. On an inter-state sale the same total amount is charged as a single IGST instead of being split, so the figure here is still the tax you owe — only the label and the split change.
GST Calculator examples
Add 18% GST to ₹1,000
GST ₹180 · CGST ₹90 · SGST ₹90 · Total ₹1,180
Reverse GST: find the tax inside a ₹1,180 inclusive total at 18%
Base ₹1,000 · GST ₹180 — not ₹212.40, which is what subtracting 18% from the total would give
MRP ₹599 at 12%, tax already included
Base ₹534.82 · GST ₹64.18
Add 5% GST to ₹2,400
GST ₹120 · CGST ₹60 · SGST ₹60 · Total ₹2,520
Limitations & privacy
This calculates standard single-rate GST only. It does not handle mixed-rate invoices, the composition scheme, reverse charge, input tax credit, or exemptions. It shows the intra-state CGST and SGST split; for an inter-state sale read the same GST amount as IGST, which is not split. Rates differ by goods and service and change over time, so confirm the rate and scheme that apply to yours rather than assuming a slab.
Inputs and results stay in this browser. Only tool identifiers are stored for your recently used tools. You can clear that history from the directory.
GST Calculator: frequently asked questions
What is the reverse GST formula?
Base price = total ÷ (1 + rate ÷ 100). At 18%, divide the inclusive total by 1.18. The GST is the total minus that base price. Subtracting the rate from the total is the common mistake and gives a number that is too low, because the rate was applied to the base price, not to the total.
How do I calculate GST on an MRP?
MRP is the maximum retail price and already includes GST, so use the reverse calculation rather than adding. Enter the MRP as the inclusive total with the applicable rate, and the tool shows how much of it is tax.
What is the difference between CGST, SGST and IGST?
On a sale within one state the GST is split evenly into CGST for the centre and SGST for the state. On a sale between states the same amount is charged once as IGST, with no split. The total tax is the same either way; this tool shows the CGST and SGST halves, so for an inter-state invoice read the full GST amount as IGST.
Which GST rate applies to what I am selling?
That depends on the goods or service and changes over time. The common slabs are 5%, 12%, 18% and 28%, with other rates for particular categories. Confirm the current rate for your item rather than assuming — the calculator accepts any rate you enter.
Which mode should I use for a shop receipt?
If the printed price already includes tax, use the reverse direction to see how much of it is GST. If you are quoting a price before tax, use the adding direction.
Can I use a custom GST rate?
Yes. Enter any rate rather than picking a slab, which is what you need for categories outside the four common ones.
Updated October 10, 2026