Enter an amount, pick a GST rate and choose whether the supply is within your state or across state lines. Lekhiva's GST calculator instantly splits the tax into CGST, SGST or IGST — no sign-up required.
Select a verified rate. SGST is replaced by UTGST where applicable. Cess is excluded; totals are rounded for display. This tool does not determine tax applicability.
GST calculation formulas
The calculator uses two standard formulas depending on whether your amount already includes tax:
- Exclusive of GST (tax added on top): GST = Taxable value × (Rate ÷ 100). Total = Taxable value + GST.
- Inclusive of GST (reverse GST calculation, working backwards from a tax-included total): Taxable value = Total ÷ (1 + Rate ÷ 100). GST = Total − Taxable value.
Worked example at 18%: a taxable value of ₹10,000 (exclusive) produces GST of ₹1,800 and a total of ₹11,800. Run the same figures the other way — a total of ₹11,800 already inclusive of 18% GST — and the calculator recovers the same ₹10,000 taxable value and ₹1,800 tax, just approached in reverse.
Choose the rate for your transaction
The September 2025 reform introduced a broad 5% and 18% structure and a special 40% rate for selected supplies. Exceptions and special rates exist. Check the applicable notification, classification and transaction date rather than treating a preset as a rate recommendation.
This calculator offers 0%, 5%, 18% and 40% presets plus a custom rate. Use the custom field for a verified special rate or a historical calculation. A zero tax calculation does not distinguish exempt, nil-rated and zero-rated supplies, which can have different legal consequences. Cess is not included.
Reference: Ministry of Finance FAQs on the September 2025 changes. For your actual invoice, confirm the current notification and any subsequent amendments.
When to charge CGST + SGST or IGST
GST is a destination-based tax, so the split depends on where the supply is made — not simply where the payment is collected from. Compare the supplier's registered state with the legally determined place of supply:
- Use Within state when the supplier and the place of supply are in the same state. The rate splits equally between CGST (to the Centre) and SGST (to the state).
- Use Other state when the supplier and the place of supply are in different states or Union Territories. The full rate applies as a single IGST charge, collected by the Centre and apportioned to the destination state.
For example, an 18% intra-state invoice shows 9% CGST plus 9% SGST, while an ordinary inter-state supply at the same rate shows 18% IGST. In applicable Union Territories, UTGST replaces SGST. Read the introductory CGST, SGST and IGST explainer. Exports, SEZ supplies and other special cases require separate treatment; this calculator does not determine eligibility or exemptions.
Frequently asked questions
How do I calculate GST from a total that already includes tax?
Divide the total by (1 + rate ÷ 100) to recover the taxable value, then subtract it from the total to get the GST. For example, ₹11,800 inclusive of 18% GST is ₹10,000 taxable value plus ₹1,800 tax. Choose "Inclusive of GST" in the calculator to do this automatically.
How is GST split between CGST and SGST?
Equally. An 18% intra-state supply shows 9% CGST and 9% SGST on the invoice. When the supply is inter-state, the full 18% is charged as IGST instead. The split depends on the supplier's state and the place of supply, not on where payment comes from.
What are the GST rates after the September 2025 change?
The reform introduced a broad structure of 5% and 18%, with a special 40% rate for selected supplies and some special rates alongside. Many items previously at 12% or 28% moved into the new slabs. Always confirm the current rate and classification for your specific goods or service before invoicing.
Are the 12% and 28% GST slabs still applicable?
For most goods and services, no — the September 2025 structure moved most supplies to 5% or 18%, with a special 40% rate for selected items. Exceptions and special rates exist, so use the custom-rate field for a verified special rate or a historical calculation.
Does this GST calculator store my figures?
No. Calculations run entirely in your browser; nothing you enter is sent to a server or stored. Refreshing the page clears everything.
Can I use this for a reverse GST calculation?
Yes. Select "Inclusive of GST", enter the tax-inclusive total and the rate, and the calculator works backwards to show the taxable value and the exact tax amount, including the CGST/SGST or IGST split.