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Invoicing, margin & GST calculators
GST Calculator
Add, reverse & split GST (CGST/SGST/IGST) at current GST 2.0 rates. Accurate, instant and free — for India.
What these mean:
What these mean:
Adding 18% GST (intra-state → CGST+SGST).
Net amount
₹1,000
Total GST
₹180
CGST · 9%
₹90
SGST · 9%
₹90
Gross amount
₹1,180
CGST + SGST vs IGST
Need a full GST tax invoice? Use the Invoice Generator. Outside India, try the VAT Calculator or Sales Tax Calculator.
Add GST vs reverse GST
GST (Goods & Services Tax) is India's destination-based indirect tax on the supply of goods and services. There are two everyday calculations: adding GST to a pre-tax price, and reversingit out of a GST-inclusive total. The reverse case is the one people get wrong — you divide the rate out, you don't subtract it.
Add GST
net → gross
gross = net × (1 + rate ÷ 100)
₹1,000 at 18% → GST ₹180, gross ₹1,180.
Reverse GST
gross → net
net = gross × 100 ÷ (100 + rate)
₹1,180 at 18% → base ₹1,000, GST included ₹180. Not gross − 18%.
- 1Split an intra-state supply into CGST + SGST: 18% GST on ₹1,000 = ₹180, split equally into ₹90 CGST and ₹90 SGST. Sell inter-state and the same ₹180 becomes a single ₹180 IGST.
- 2Turn it into a compliant document: Drop these figures into the Invoice Generator to produce a Rule-46 GST tax invoice with the CGST/SGST/IGST breakdown and download it as a PDF.
CGST/SGST vs IGST, and the GST 2.0 slabs
The place of supply decides the split. Same state (intra-state) → the tax divides into CGST (centre) and SGST (state), each half the rate. Different states or an import (inter-state) → a single IGST at the full rate. The total tax is the same; only who collects it changes.
GST 2.0 — four headline slabs
Section 50 interest on unpaid GST
Paying GST late attracts interest under Section 50 of the CGST Act: interest = tax × rate × days ÷ 365. The rate is 18% p.a. for ordinary late payment (Section 50(1)), rising to 24% p.a. where input tax credit was wrongfully availed and utilised (Section 50(3)). For example, ₹50,000 of tax paid 30 days late at 18% is about ₹739.73 of interest.
Frequently asked questions
Multiply the net (pre-tax) amount by the GST rate and add it back: gross = net × (1 + rate ÷ 100). For example, ₹1,000 at 18% GST becomes ₹1,000 + ₹180 = ₹1,180. On an intra-state sale the ₹180 splits into ₹90 CGST and ₹90 SGST; on an inter-state sale it is a single ₹180 IGST.
Do not simply subtract the rate — divide it out. The pre-tax base = gross × 100 ÷ (100 + rate). For ₹1,180 at 18%, the base is 1,180 × 100 ÷ 118 = ₹1,000, and the GST included is ₹180. Subtracting 18% of ₹1,180 (₹212.40) would be wrong.
For an intra-state supply (buyer and seller in the same state) the GST is split equally into CGST (collected by the central government) and SGST (collected by the state) — so 18% GST is 9% CGST + 9% SGST. For an inter-state supply (different states, or an import) the whole tax is a single IGST at the full rate. The total tax paid is identical; only the split differs.
Since 2025-09-22, GST 2.0 uses four headline slabs: 0% (nil/exempt), 5% (merit), 18% (standard) and 40% (sin and luxury goods). The old 12% and 28% slabs were removed for most items — many 28% goods (small cars, air conditioners, cement, large TVs) dropped to 18%, and several 12% items (butter, ghee, packaged snacks) dropped to 5%. A few niche rates remain, e.g. 3% on gold/jewellery and 0.25% on rough diamonds.
Under Section 50(1) of the CGST Act, unpaid GST attracts interest at 18% per annum, charged on the tax due for the number of days it is late: interest = tax × 18% × days ÷ 365. Where input tax credit was wrongfully availed and utilised, Section 50(3) raises the rate to 24% per annum.
Yes — it is completely free with no sign-up, and every calculation runs in your browser. Nothing you type is sent to a server or stored. Rates are for guidance; confirm the exact HSN/SAC rate and place-of-supply treatment for your transaction before filing.
Method, assumptions & references
Methodology: adding GST → gross = net × (1 + rate/100); reversing GST → net = gross × 100 / (100 + rate). Intra-state supply splits into CGST + SGST (half the rate each); inter-state supply is a single IGST at the full rate. GST 2.0 headline slabs (0/5/18/40%) are effective 2025-09-22. Section 50 interest = tax × rate × days / 365 at 18% (50(1)) or 24% (50(3)). Slab data is versioned in-repo and PR-updated on rate changes (repo-json-on-rate-change).
Cross-links
How we calculate this
Reviewed by Reckonist Editorial · Last reviewed 4 July 2026. Figures follow the methods and sources set out in our editorial standards.
GST rates and rules change frequently; the slabs shown reflect GST 2.0 effective 22 September 2025. Figures are for guidance only — confirm the exact HSN/SAC rate and place-of-supply treatment for your transaction before filing. This is not tax advice.
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