GST Calculator (India)
This GST calculator works out Indian Goods and Services Tax both ways — adding GST to a taxable value, or reversing it out of a GST-inclusive amount. Choose intra-state to see the CGST and SGST halves as they must appear on the invoice, or inter-state for a single IGST line, and add compensation cess where the goods attract it.
The taxable value before tax is added.
The slab for that HSN or SAC code. 5, 18 and 40 are the principal rates after the September 2025 rationalisation; 12 and 28 still apply to earlier invoices and credit notes.
Charged over and above the slab, on demerit goods only. Leave at 0 for everything else.
A discount shown on the invoice itself reduces taxable value under section 15(3).
Incidental charges form part of taxable value under section 15(2) — they are taxed, not added after tax.
At a glance
How the gst calculator works
- 1 Choose whether you are adding GST to a pre-tax value or reversing it out of a GST-inclusive total. The reverse calculation is not a subtraction — it divides — which is where most manual errors come from.
- 2 Choose intra-state or inter-state. This is decided by the place of supply, not by where the buyer is registered or where the invoice is posted.
- 3 Enter the amount and the slab for the HSN or SAC code being supplied. Add compensation cess only if the goods attract it.
- 4 When adding GST, enter any invoice discount and any freight, packing or insurance charged — the first reduces taxable value, the second increases it.
- 5 The result gives taxable value, the tax split across the correct heads, and the invoice total. Round the tax to the nearest rupee when you post it.
Taxable value (adding GST) = amount − discount shown on the invoice + freight, packing and other incidental charges. GST = taxable value × rate ÷ 100. Intra-state: CGST = SGST = GST ÷ 2. Inter-state: IGST = the whole GST. Cess = taxable value × cess rate ÷ 100. Invoice total = taxable value + GST + cess. Reversing GST out of an inclusive amount: taxable value = amount × 100 ÷ (100 + rate + cess rate).
Worked example
A Maharashtra supplier bills a Maharashtra customer ₹2,50,000 for goods at 18% GST, allows a 5% trade discount of ₹12,500 on the invoice, and charges ₹4,000 of freight. Because both parties are in the same state, the tax splits into CGST and SGST.
- ·Amount before GST: ₹2,50,000
- ·Trade discount on invoice: ₹12,500
- ·Freight and packing: ₹4,000
- ·GST rate: 18%
- ·Supply: intra-state
- ·Cess: nil
- 1. Taxable value = 2,50,000 − 12,500 + 4,000 = ₹2,41,500
- 2. Total GST = 2,41,500 × 18% = ₹43,470
- 3. CGST = 43,470 ÷ 2 = ₹21,735
- 4. SGST = 43,470 ÷ 2 = ₹21,735
- 5. Invoice total = 2,41,500 + 43,470 = ₹2,84,970
Taxable value ₹2,41,500 · CGST ₹21,735 · SGST ₹21,735 · invoice total ₹2,84,970.
Two things are worth noting. The freight is inside the taxable value, not added after tax — charging GST on ₹2,37,500 and then adding ₹4,000 of freight would understate the tax by ₹720 and make the invoice wrong. And reversing the total back out shows why the inclusive calculation must divide: ₹2,84,970 × 100 ÷ 118 returns ₹2,41,500 exactly, whereas deducting 18% from the total gives ₹2,33,675 — understating the taxable value by ₹7,825 and the tax with it.
GST compliance this calculator follows
The arithmetic here is only useful if it matches what the law requires on the invoice. These are the rules the calculation is built on, and the ones to check before you file.
Which tax heads apply is decided by place of supply, not by the buyer address
If the place of supply falls in the same state or Union Territory as the supplier, the tax is CGST plus SGST in equal halves. If it falls in a different state or UT, or the supply is an import or to an SEZ, it is IGST in full. Getting this wrong is not a rounding error — it means tax paid under the wrong head, which has to be corrected and re-paid rather than simply adjusted.
Sections 10 to 13, IGST Act 2017
Union Territories without a legislature charge UTGST, not SGST
In UTs that have no legislature the state half is levied as UTGST at the same rate, so an 18% intra-UT supply is CGST 9% plus UTGST 9%. Delhi, Puducherry and Jammu & Kashmir have legislatures and charge SGST. The amount is identical; the head on the invoice is not.
UTGST Act 2017
Taxable value includes incidental charges and excludes invoice discounts
Transaction value is the price actually paid, plus any incidental expenses charged to the recipient — packing, freight, insurance, commission — and plus any tax other than GST. A discount is deducted only if it is shown on the invoice itself, or, for a post-supply discount, was agreed before the supply and can be linked to it. This is why freight belongs inside the taxable value rather than being added after tax.
Section 15, CGST Act 2017
Tax is rounded to the nearest rupee
The tax, interest, penalty or refund figure is rounded to the nearest rupee, with 50 paise and above rounded up. Round the tax amount, not the underlying taxable value, and round each tax head separately so the CGST and SGST lines still sum to the total shown.
Section 170, CGST Act 2017
CGST and SGST must be shown as separate lines on the invoice
A tax invoice has to carry the supplier name, address and GSTIN; a consecutive serial number of not more than sixteen characters; the date; the recipient details; the HSN or SAC code; description, quantity and taxable value; the rate and amount of each tax head separately; the place of supply for inter-state supplies; and a signature or digital signature. A single combined "GST 18%" line on an intra-state invoice is not compliant.
Rule 46, CGST Rules 2017
HSN or SAC digits depend on your turnover
Taxpayers with aggregate annual turnover up to ₹5 crore report four-digit HSN on B2B invoices, and those above ₹5 crore report six digits. The code drives the rate, so an incorrect HSN produces an incorrect tax however sound the arithmetic. Eight digits apply to specified exports and notified goods.
Notification 78/2020 – Central Tax
E-invoicing is mandatory above ₹5 crore turnover
Businesses whose aggregate annual turnover exceeds ₹5 crore in any financial year from 2017-18 onwards must generate B2B invoices through the Invoice Registration Portal and obtain an IRN. An invoice in that bracket without a valid IRN is not treated as a valid tax invoice, which puts the recipient input tax credit at risk as well as your own compliance.
Movement of goods over ₹50,000 needs an e-way bill
A consignment whose value exceeds ₹50,000 requires an e-way bill generated before movement begins, whether the movement is inter-state or intra-state and whether or not it follows a supply. Consignment value for this threshold includes the tax, so the invoice total from this calculator is the figure to test against ₹50,000 — not the taxable value.
Rule 138, CGST Rules 2017
Composition dealers must not charge GST on the invoice
A person paying tax under the composition scheme pays a flat rate on turnover — broadly 1% for traders and manufacturers, 5% for restaurant services and 6% for other specified services — and cannot collect tax from the customer or claim input tax credit. Their bill of supply must carry the declaration that they are a composition taxable person and not eligible to collect tax. This calculator computes normal-scheme GST and does not apply to them.
Section 10, CGST Act 2017
Under reverse charge the tax is the same but the payer is not
For notified supplies, and for certain purchases from unregistered suppliers, the recipient pays the GST directly to the government instead of the supplier collecting it. The amount is exactly what this calculator produces; what changes is who deposits it, and that the recipient claims the credit against their own payment rather than against a supplier invoice.
Sections 9(3) and 9(4), CGST Act 2017
Input tax credit is set off in a fixed order
IGST credit must be used against IGST liability first, and only the balance may go against CGST and then SGST. CGST credit cannot be set against SGST, or the reverse. The order is not optional, and getting it wrong is a common cause of a cash payment that was not actually due.
Section 49 and Rule 88A, CGST Rules 2017
What you calculate has to match what you file
Outward supplies are reported invoice-wise in GSTR-1 and the summary liability with credit set-off in GSTR-3B. The tax head split from this calculator is what appears in both, so an intra-state supply misclassified as inter-state will not simply net off — it needs an amendment in a later return, and any short payment carries interest.
Rates and thresholds change. The GST Council rationalised the slabs in September 2025, with 5% and 18% as the principal rates and 40% on selected demerit goods, and 12% and 28% items largely remapped — but the rate that applies is always the one notified for your specific HSN or SAC on the date of supply. Treat this calculator as arithmetic you can audit, not as tax advice, and confirm the rate, the place of supply and your scheme with a practitioner before filing.
Frequently asked questions
How do you calculate GST on an amount?
Multiply the taxable value by the rate and divide by 100: ₹2,41,500 at 18% gives ₹43,470 of GST and a total of ₹2,84,970. For an intra-state supply that ₹43,470 splits into CGST ₹21,735 and SGST ₹21,735, both shown separately on the invoice; for an inter-state supply the whole ₹43,470 is IGST. The taxable value itself is the price less any discount shown on the invoice, plus freight, packing and other incidental charges.
How do I remove GST from an inclusive amount?
Divide, do not subtract. Taxable value = inclusive amount × 100 ÷ (100 + rate), so ₹2,84,970 at 18% gives ₹2,41,500 and the GST is the ₹43,470 difference. Deducting 18% from the inclusive figure instead gives ₹2,33,675 — understating the taxable value by ₹7,825. The error grows with the rate: at 28% subtracting rather than dividing is out by more than 7%.
What is the difference between CGST, SGST and IGST?
They are the same tax collected by different governments. On a supply within one state the slab splits equally between CGST, which goes to the Centre, and SGST, which goes to that state — 18% becomes 9% plus 9%. On a supply between states the whole 18% is charged as IGST, collected by the Centre and later apportioned. The total the customer pays is identical either way; only the heads differ.
What are the current GST rates in India?
Following the GST Council rationalisation of September 2025 the principal slabs are 5% and 18%, with a 40% rate on selected demerit and luxury goods, alongside nil-rated and exempt supplies. Items formerly at 12% and 28% were largely remapped into the two main rates. Special rates remain for a few categories, such as 3% on gold and silver and 0.25% on rough diamonds. Because the rate follows the HSN or SAC code, always confirm the notified rate for the specific goods or service on the date of supply.
When is IGST charged instead of CGST and SGST?
Whenever the place of supply is in a different state or Union Territory from the supplier, and also on imports, on supplies to and from Special Economic Zones, and on exports, which are zero-rated. The test is place of supply under sections 10 to 13 of the IGST Act — not the buyer billing address, not where the goods were ordered from, and not where the payment came from.
Is GST charged on freight and packing?
Yes. Incidental expenses including packing, freight, insurance and commission charged to the recipient form part of the taxable value under section 15(2), so they are taxed at the same rate as the supply rather than added on after tax. Adding freight after computing the tax is one of the most common invoicing errors and always understates the liability.
What is compensation cess and when does it apply?
A separate levy charged over and above the GST slab on a narrow list of demerit and luxury goods, historically including tobacco products, aerated drinks, coal and certain motor vehicles. It is calculated on the same taxable value as GST but shown as its own line, and it is not eligible for set-off against ordinary GST liability — cess credit can only be used against cess. Leave the cess field at zero for everything else.
How should GST be rounded on an invoice?
To the nearest rupee, with 50 paise and above rounded up, under section 170 of the CGST Act. Round the tax figure rather than the taxable value, and round each head separately so that the CGST and SGST lines still add up to the total tax shown. Small differences between your books and the portal usually trace to rounding applied at a different step.
Do I need to register for GST?
Registration is compulsory once aggregate turnover crosses ₹40 lakh for goods or ₹20 lakh for services, reduced to ₹20 lakh and ₹10 lakh respectively in the special category states. It is compulsory regardless of turnover for inter-state suppliers of goods, e-commerce operators, persons liable under reverse charge and casual or non-resident taxable persons. Voluntary registration is allowed and is often worth it where your customers need the input credit.
Can I use this calculator if I am under the composition scheme?
No. A composition taxpayer pays a flat percentage of turnover — broadly 1% for traders and manufacturers, 5% for restaurant services, 6% for other specified services — and is prohibited from collecting GST from customers or claiming input tax credit. Their document is a bill of supply carrying the composition declaration, not a tax invoice. This calculator computes normal-scheme GST with the CGST, SGST and IGST split, which does not apply to them.
Does this calculator handle reverse charge?
The amount is the same, so yes for the arithmetic. Under reverse charge the recipient rather than the supplier deposits the tax, and the supplier invoice carries no GST but must state that tax is payable on reverse charge. Use the same rate and taxable value here; just remember the liability sits with the buyer, who pays it in cash and then claims the credit separately.