GST Calculator (Inclusive & Exclusive)
Forward (exclusive) or reverse (inclusive) GST with intra-state (CGST + SGST) and inter-state (IGST) split for 0%, 5%, 12%, 18%, 28% slabs.
GST Rate Slabs
Supply Type
Taxable Value
₹10,000.00
CGST (9%)
₹900.00
SGST (9%)
₹900.00
Total GST Amount
₹1,800.00
Final Invoice Total
₹11,800.00
Amount in Words: Rupees Eleven Thousand Eight Hundred Only
How Goods & Services Tax (GST) is Calculated in India
Understand the exact mathematical formulas for forward (exclusive) and reverse (inclusive) tax computation under the CGST & IGST Acts.
1. Forward vs Reverse GST Calculation Formulas
Mathematical proof and standard accounting implementation
Applied when quoting a net taxable base price and appending statutory GST at the end of the bill.
GST Amount = (Base × Rate) ÷ 100
Total Invoice = Base + GST Amount
Example: ₹10,000 base with 18% GST → ₹1,800 tax = ₹11,800 total.
Used to determine the original taxable base when prices are stated inclusive of all statutory taxes.
Base Value = (Gross × 100) ÷ (100 + Rate)
GST Amount = Gross − Base Value
Example: ₹1,180 retail MRP with 18% GST → ₹1,000 base + ₹180 tax.
2. Official Indian GST Rate Slabs (2026 CBIC Schedule)
Statutory categories established by the GST Council
Fresh fruits, unbranded flour (atta), fresh milk, salt, organic fertilizers, judicial papers.
Packaged food items, edible oils, tea, coffee, life-saving medicines, apparel under ₹1,000.
Processed foods, fruit juices, dairy products (butter, cheese), business software, non-AC dining.
Software development, IT consulting, capital goods, financial services, telecom, industrial equipment.
Automobiles, air conditioners, aerated drinks, cement, luxury hospitality (+ Cess).
3. Intra-State vs Inter-State Tax Jurisdiction
Determined strictly by the 2-digit state code of Supplier and Place of Supply
Intra-State Supply (Same State)
If the supplier's registered address and the recipient's Place of Supply (POS) are located in the same state (e.g., Maharashtra 27 to Maharashtra 27), tax is split into CGST (50%) and SGST (50%).
Inter-State Supply (Different State)
If goods or services travel across state borders (e.g., Delhi 07 to Karnataka 29), Integrated GST (IGST) is charged at the full 100% rate with no CGST/SGST split.
Ready to turn this calculation into a tax invoice?
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GST Calculator FAQs
Common questions regarding tax calculation rules and compliance in India
When adding GST to a net taxable value: GST Amount = (Taxable Amount × GST Rate) ÷ 100. The Total Gross Invoice Amount = Taxable Amount + GST Amount. For example, on a ₹10,000 professional fee at 18% GST, the GST is ₹1,800, bringing the final payable total to ₹11,800.