GST Calculator India – Free Online Tool

GST Calculator India – And Why CGST+SGST Isn't the Same Thing as IGST

By the CSC Tool Hub editorial team · Last reviewed September 2026

CSC Tool Hub's GST Calculator computes GST in exclusive or inclusive mode and shows the CGST/SGST/IGST breakdown for reference. One thing worth being precise about: a real transaction never has both CGST+SGST and IGST applied — it's always one or the other, decided by where the buyer and seller are located. This page explains exactly how to pick the right one.

How to Know Whether to Charge CGST+SGST or IGST

Situation	What applies
Supplier's registered state = place of supply (usually the buyer's state)	CGST + SGST, each half of the total GST rate
Supplier's registered state ≠ place of supply	IGST alone, at the full GST rate

Example: an 18% GST sale within Maharashtra (both supplier and buyer registered in Maharashtra) charges 9% CGST + 9% SGST. The same sale from Maharashtra to a buyer in Karnataka charges 18% IGST instead — not both sets of tax.

Common GST Rate Slabs — What Actually Falls Where

Rate	Typical category	Example
5%	Essential goods, some food items, basic household items	Packaged food staples, footwear under a price threshold
12%	Processed foods, some manufactured goods	Processed food products, certain apparel
18%	Standard rate — most goods and services	Most consumer electronics, professional services, restaurants (non-AC in some cases differ)
28%	Luxury and sin goods	Luxury cars, tobacco products, aerated drinks

These are general patterns, not a definitive lookup — actual rates depend on the specific HSN (for goods) or SAC (for services) code, which can place similar-seeming products in different slabs. Always confirm against the current official GST rate schedule for your exact product or service code before invoicing.

GST Calculation Formula

• Exclusive GST (adding tax to a base price): GST Amount = (Original Cost × GST%) ÷ 100; Total = Original + GST.
• Inclusive GST (extracting tax from a tax-included total): Original = (Total × 100) ÷ (100 + GST%); GST = Total − Original.

A common mistake with inclusive calculations: subtracting the GST percentage directly from the total (e.g., Total − 18% of Total) instead of using the formula above — this understates the original amount because the 18% was calculated on the original price, not the tax-inclusive total.

How to Use This GST Calculator

1. Enter Amount and GST Rate (use the quick-rate buttons for 5/12/18/28%).
2. Select Exclusive or Inclusive depending on whether your amount already includes GST.
3. Calculate to see the original amount, GST, and total.
4. Pick CGST+SGST or IGST from the reference split based on whether the transaction is intra-state or inter-state, using the table above.

Key Features

Common Mistakes

• Charging both CGST+SGST and IGST on the same invoice — only one path ever applies, based on the place of supply.
• Subtracting the GST percentage directly for inclusive calculations instead of using the correct division formula.
• Assuming a product category always maps to one GST slab — the actual rate is determined by the specific HSN/SAC code, which can vary within a broad category.

Common Use Cases

• Retail pricing: calculating the final price of a product including GST.
• Invoice verification: checking whether a supplier applied CGST+SGST or IGST correctly for the transaction type.
• E-commerce pricing: setting product prices with GST included.
• Extracting the base price from a GST-inclusive quoted amount.

Privacy and Security

All calculations run locally in your browser. Your amounts and calculation history are stored only in your browser's local storage, never uploaded to any server.

About CSC Tool Hub

CSC Tool Hub builds free browser-based calculators — this GST calculator, a percentage calculator, an EMI calculator, a CGPA calculator and more.

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