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.

GST calculatorNo sign-up required
₹
₹
GST rate
Amount type
Supply type
Taxable value₹10,000.00
CGST · 9%₹900.00
SGST · 9%₹900.00
Total amount₹11,800.00

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.

Next: See the full GST invoice checklist →