Enter an amount that already has GST inside it and get the taxable value and the tax back out, split the way an invoice has to show them. It works the other way too, if you have a figure that excludes tax and want the total.
Nothing you type here is sent anywhere. The arithmetic happens in this tab and is gone when you close it.
GST is charged on the taxable value, not on the total, so getting it back out of a tax-inclusive figure means dividing rather than taking a percentage. Taking 18% of ₹5,900 gives ₹1,062, which is wrong — the right answer is ₹900, because ₹5,900 is already 118% of the taxable value.
Divide by 1 plus the rate: ₹5,900 ÷ 1.18 = ₹5,000 taxable, and the ₹900 difference is the tax. On an intra-state supply that ₹900 appears on the invoice as CGST ₹450 and SGST ₹450, each computed at half the rate. On an inter-state supply the same ₹900 appears once, as IGST.
This calculator computes each half separately and adds them, rather than halving the combined figure. On some amounts those two methods differ by a paise, and since the two components are meant to be equal, the second one produces an invoice that reconciles as a total but not as a summary.
Most services are 18%. The remaining slabs are 5% for a lot of essentials and transport, 12% for a middle band that includes some processed food and job work, and 28% for luxury and sin goods. Two special rates sit outside that: 3% on gold, silver and jewellery, and 0.25% on rough diamonds and similar stones.
One caveat worth knowing: several 28% items also carry a compensation cess on top, which is a separate levy at its own rate. This calculator works on GST alone, so if the amount you are unpicking included cess, the figure it gives you for the taxable value will be too high.
Divide the total by 1 plus the rate, and whatever is left over is the tax. At 18%, a total of ₹5,900 divided by 1.18 gives a taxable value of ₹5,000, so the GST inside it is ₹900. The calculator on this page does that and splits the result into CGST and SGST, or into IGST.
Taxable value = total ÷ (1 + rate ÷ 100), and GST = total − taxable value. At 12% that is the total divided by 1.12; at 28% it is the total divided by 1.28. Going the other way, from a figure that excludes tax, GST = taxable value × rate ÷ 100.
Yes. They are two separate levies at half the rate each, and they have to be equal on the invoice. Halving one combined figure can leave the two components a paise apart, which reconciles as a total but does not match what a GSTR-1 summary expects, so this calculator rounds each half itself and adds them.
If you are working a figure backwards because you have to raise a document for it, the GST invoice generator does the same arithmetic across every line, decides between CGST + SGST and IGST from the place of supply, spells the total in words, and gives you a finished PDF. There are also Excel templates if you would rather keep a file of your own.
These notes are general guidance, not tax advice. Rates change, and the treatment of a supply depends on what it is and where it is going — confirm anything you are unsure about with your accountant.
