ReckonBoxHow the GST calculator works
GST is an indirect tax charged on a single transaction, and it can either be added to a price that excludes it or pulled back out of a price that already includes it. This calculator does both, on the slabs in force since 22 September 2025, and splits the tax the way an invoice must: CGST plus SGST within a state, UTGST in a Union Territory, or a single IGST across states.
Take the default. On a Rs 1,000 taxable value at 18%, the GST is Rs 180 and the invoice total is Rs 1,180. Since that is an intra-state supply, the Rs 180 splits into Rs 90 CGST and Rs 90 SGST, which is what your invoice has to show. Flip the mode to remove and enter Rs 1,180, and the same Rs 180 comes back out.
The rates that actually apply now
Since 22 September 2025 the GST slabs are nil, 5%, 18% and 40%, following the 56th GST Council: a merit rate of 5%, a standard rate of 18%, and a de-merit rate of 40% for a select few goods. The old 12% and 28% slabs are gone for most goods, which matters more than it sounds. Nine of the thirteen Indian calculators we checked still offer 12% or 28%, ten months on, so it's easy to compute a rate that no longer legally exists.
This tool lists only the four current slabs. A custom-rate field covers the edge cases, such as recomputing an old invoice, without pretending an abolished slab is still live.
Adding and removing GST
To add GST, the tax is the taxable value times the rate divided by 100; to remove it, the tax is the gross price times the rate divided by 100 plus the rate. The second one trips people up, because taking 18% off a GST-inclusive price isn't the same as dividing by 1.18 in your head and rounding.
| Direction | Formula | On the default |
|---|---|---|
| Add GST | value x rate / 100 | Rs 1,000 x 18 / 100 = Rs 180 |
| Remove GST | gross x rate / (100 + rate) | Rs 1,180 x 18 / 118 = Rs 180 |
Both land on the same Rs 180, which is the check worth doing whenever an inclusive figure looks off.
CGST, SGST, UTGST and IGST
A supply within one state carries CGST and SGST, each at exactly half the total rate, while a supply across states carries IGST at the full rate instead. So 18% is 9% plus 9% inside a state, and a single 18% when the goods cross a state line. A Union Territory works like an intra-state supply, with UTGST standing in for SGST.
The halving is not a convention someone invented. It's visible in the law: the CGST Act caps CGST at 20% while the IGST Act caps at 40%, exactly twenty plus twenty, and CBIC's own rate schedules are published at 2.5, 9 and 20, precisely half of 5, 18 and 40.
What changed on 22 September 2025
The 56th GST Council collapsed the four old slabs into two, moving hundreds of items down: 28% to 18% on air conditioners, televisions, cement and small cars, and 12% to 5% on tractors, bicycles and most food. Some items went to nil, including 33 lifesaving drugs from 12% and UHT milk, paneer and Indian breads from 5%. The table above applies those moves to your own amount, so you can see what the same purchase costs now against what it used to.
Compensation cess is ending too, merged into the 40% rate, which is why mid-size and large cars are now 40% with no cess on top. One carve-out survives, and every ranked calculator misses it: pan masala, gutkha, cigarettes, zarda, unmanufactured tobacco and bidi stay on their old rates plus cess until the cess loan obligations are discharged, and they are taxed on retail sale price rather than transaction value. The calculator flags this whenever you select 40%.
What this does not cover
This calculator handles the tax on one transaction: the slab, the split, and the arithmetic in both directions. It doesn't decide the right slab for your product, which turns on the HSN or SAC classification and is where most GST disputes actually live. It also does not handle input tax credit, reverse charge, e-invoicing, place-of-supply edge cases, or whether you need to register at all. Rates move when the Council meets, so the 22 September 2025 structure is what this page reflects. Treat the figure as arithmetic, not tax advice, and confirm your classification and filing with a chartered accountant or a GST practitioner.
Frequently asked questions
What are the GST rates in India now? Since 22 September 2025 the GST slabs are nil, 5%, 18% and 40%, following the 56th GST Council. It is a two-rate structure, a merit rate of 5% and a standard rate of 18%, plus a 40% de-merit rate for a few goods such as large cars and tobacco-class items, and the old 12% and 28% slabs no longer apply to most goods.
How do I calculate GST on an amount? To add GST, the GST amount is the taxable value times the rate divided by 100, and the total is the value plus that GST. On Rs 1,000 at 18% the GST is Rs 180 and the invoice total is Rs 1,180.
How do I remove GST from an inclusive price? To pull GST out of a price that already includes it, GST equals the gross price times the rate divided by 100 plus the rate. On a Rs 1,180 inclusive price at 18%, the GST is 1,180 times 18 divided by 118, which is Rs 180, leaving a taxable value of Rs 1,000.
What is the difference between CGST, SGST and IGST? A supply within one state carries CGST and SGST, each at half the total rate, so 18% becomes 9% CGST plus 9% SGST. A supply across states carries IGST at the full rate instead, so 18% is a single 18% IGST. In a Union Territory, UTGST takes the place of SGST.
Are the 12% and 28% GST slabs gone? Yes, the 12% and 28% slabs were removed for most goods on 22 September 2025, with items moving down to 5% or 18% and a few de-merit goods moving to 40%. Many calculators still offer 12% and 28%, which now produce the wrong tax for most goods, so this tool lists only the current slabs and keeps a custom-rate field for old invoices.
Is compensation cess still charged? The compensation cess levy is ending and its rate has been merged into GST, which is why the de-merit rate is 40%, per the GST Council FAQ. Mid-size and large cars, for example, are now 40% with no cess. The exception is the tobacco basket, which still carries cess until the cess loan obligations are discharged.
Do cigarettes and pan masala use the 40% rate? Not yet. Pan masala, gutkha, cigarettes, zarda, unmanufactured tobacco and bidi stay on their existing rates plus compensation cess until the loan and interest obligations of the cess account are discharged, and they are taxed on retail sale price rather than transaction value. The calculator flags this when you pick 40%.
Who has to charge GST? Businesses registered under GST charge it on their taxable supplies and report it in their returns, which is why the split between CGST, SGST and IGST matters on an invoice. Registration turns on turnover thresholds and the nature of the supply, so check your own position with a chartered accountant or GST practitioner.