CGST Act 2017: s.9 · IGST Act 2017: s.5 · Intra-state (CGST+SGST) and Inter-state (IGST) split
This GST Calculator helps businesses, CAs, and taxpayers quickly compute the Goods and Services Tax (GST) on any transaction. It works in two modes: adding GST to a base (exclusive) price to get the invoice value, or removing GST from an inclusive (MRP) price to find the taxable value and tax component.
Under the GST framework (CGST Act 2017 and IGST Act 2017), tax is levied under three heads. For intra-state supplies (buyer and seller in the same state), GST is split equally into CGST (Central GST) and SGST/UTGST (State/Union Territory GST). For inter-state supplies (different states, or imports), the entire GST is levied as IGST (Integrated GST).
All GST rates in India fall under one of the notified slabs: 0%, 0.25%, 3%, 5%, 12%, 18%, or 28%. The applicable rate for any supply is determined by the HSN code (for goods) or SAC code (for services). This calculator supports all standard slabs and outputs a print-ready computation with the CGST/SGST or IGST breakdown ready for invoice verification.
Step 1 — Enter the amount: For "Add GST" mode, enter the taxable value (base price before GST). For "Remove GST" mode, enter the GST-inclusive price (MRP or total invoice amount).
Step 2 — Select the GST rate: Choose the applicable rate for the goods or services. Common rates: 18% for most professional services and goods, 5% for essential items, 28% for luxury goods.
Step 3 — Choose the operation: Select "Add GST" to calculate the invoice value from a base price. Select "Remove GST" if you have an MRP or inclusive price and want to find the taxable value and GST component (useful when claiming Input Tax Credit).
Step 4 — Select supply type: Choose "Intra-state" if buyer and seller are in the same state — tax will be split as CGST and SGST at half the GST rate each. Choose "Inter-state" if they are in different states — the full GST applies as IGST.
Step 5 — Click Compute: The calculator instantly shows the taxable value, CGST/SGST or IGST amounts, total GST, and final invoice value.
GST formula reference:
| Operation | Formula | Example @ 18% |
|---|---|---|
| Add GST | Invoice = Base × (1 + Rate/100) | ₹1,00,000 → ₹1,18,000 |
| Remove GST | Base = Inclusive × 100 / (100 + Rate) | ₹1,18,000 → ₹1,00,000 |
| CGST | CGST = GST Amount / 2 | ₹18,000 → ₹9,000 CGST |
| SGST | SGST = GST Amount / 2 | ₹18,000 → ₹9,000 SGST |
| IGST | IGST = Full GST Amount | ₹18,000 IGST |
What is the difference between CGST, SGST, and IGST?
CGST (Central GST) and SGST (State GST) are levied simultaneously on intra-state supplies — the rate is split equally between the Centre and the state. For example, at 18% GST, CGST is 9% and SGST is 9%. IGST (Integrated GST) is levied on inter-state supplies and imports at the full rate. The IGST revenue is later apportioned between the Centre and the destination state. A supplier can never charge both IGST and CGST+SGST on the same invoice.
When should I use "Add GST" vs "Remove GST"?
Use "Add GST" when you know the taxable value (price before tax) and need to calculate the invoice amount to charge the customer — for example, when preparing a quotation or invoice. Use "Remove GST" when you have a GST-inclusive price (such as an MRP or a received invoice total) and need to split it into taxable value and GST component — for example, when booking expenses, claiming ITC, or checking if a vendor's invoice is correct.
How do I determine if a supply is intra-state or inter-state?
If the place of supply and the supplier's location are in the same state or Union Territory, it is an intra-state supply (levy CGST + SGST/UTGST). If they are in different states, or if the supply involves import or export, it is an inter-state supply (levy IGST). For services, the place of supply is determined under Sections 12 and 13 of the IGST Act, 2017, depending on whether the recipient is registered or unregistered, and the nature of the service.
What is the GST rate on CA, legal, and other professional services?
Most professional services including Chartered Accountancy, legal, consulting, IT services, management consultancy, and technical services attract GST at 18%. These fall under SAC code 9983 (other professional, technical and business services) or specific SAC codes depending on the service type. Healthcare and educational services are generally exempt from GST.
Is GST calculated on the GST amount itself?
No — GST is never charged on GST. When removing GST from an inclusive price, the correct formula is: Taxable Value = Inclusive Amount × 100 ÷ (100 + GST Rate%). This ensures GST is calculated only on the taxable value and not on itself. A common mistake is to simply apply the percentage to the inclusive amount — this calculator avoids that error automatically.
Can I use this calculator for composition scheme taxpayers?
No. Composition scheme taxpayers (Section 10 of CGST Act) pay GST at a flat rate on their turnover and cannot charge GST separately on invoices — they issue a "Bill of Supply" instead of a tax invoice, and buyers cannot claim Input Tax Credit. This calculator is for regular (non-composition) GST taxpayers who issue tax invoices. Use our Composition Scheme Calculator for composition taxpayers.
What details must a GST tax invoice contain?
Under Rule 46 of the CGST Rules, 2017, a tax invoice must include: supplier's name, address, and GSTIN; a consecutive invoice number; date of issue; recipient's name, address, and GSTIN (if registered); HSN/SAC code; description, quantity, and unit of goods/services; taxable value; the applicable GST rate; and CGST/SGST or IGST amounts shown separately. For inter-state supplies, the place of supply must also be mentioned.
What is Reverse Charge Mechanism (RCM) and does it affect this calculation?
Under Reverse Charge Mechanism (Section 9(3) and 9(4) of the CGST Act), the liability to pay GST shifts from the supplier to the recipient. Common RCM supplies include goods transport agencies, advocate services to a business, and unregistered dealer purchases beyond ₹5,000/day. In RCM cases, the recipient pays GST directly to the government — the computation formula is the same, but the supplier does not collect GST on the invoice. Use our RCM Reckoner to identify which supplies attract RCM.