Calculate GST instantly with accurate CGST, SGST and IGST breakdowns.
A clear, practical guide to understanding Indian Goods & Services Tax mathematics.
The Goods and Services Tax (GST) is India's destination-based indirect tax charged on the supply of goods and commercial services. It operates across every stage of value addition, allowing registered businesses to claim input tax credit on taxes paid during procurement, ensuring that tax is levied strictly on the incremental value created at each step.
GST-Exclusive: The listed price represents the net commercial cost before tax. The applicable tax is computed as a percentage of this figure and added to determine the gross payable total.
GST-Inclusive: The price tag reflects the total sticker price paid by the customer, already bundling the base cost and applicable tax. Sellers compute backwards to isolate their true revenue from the statutory tax liability.
Intra-State Supplies: When trading occurs within the same state, tax is split equally into CGST (Central GST) and SGST (State GST). For an 18% slab, 9% is CGST and 9% is SGST.
Inter-State Supplies: When goods or services cross state borders or are imported, IGST (Integrated GST) applies at the full statutory rate (18%) and is collected by the Central Government.
To calculate GST on a net base price:
Example: For a service engagement priced at a base fee of ₹10,000 under the 18% slab:
GST = (₹10,000 × 18) ÷ 100 = ₹1,800
Total Invoice Amount = ₹10,000 + ₹1,800 = ₹11,800
To find the pre-tax base cost from a tax-inclusive sticker price:
Example: For an electronic item bought at a retail price of ₹5,900 inclusive of 18% GST:
Base Price = (₹5,900 × 100) ÷ 118 = ₹5,000
Embedded GST = ₹5,900 - ₹5,000 = ₹900
Overview of standard tax brackets established under the national GST framework.
| GST Rate | Category & Typical Usage | Example Base (₹1,000) Calculation | Tax Split (Intra-State) |
|---|---|---|---|
| 0% | Essential food items, fresh fruits, vegetables, fresh milk, healthcare, and educational services. | Base: ₹1,000 | Tax: ₹0.00 | Total: ₹1,000.00 | CGST: 0% | SGST: 0% |
| 0.25% | Rough industrial and precious stones, unworked diamonds. | Base: ₹1,000 | Tax: ₹2.50 | Total: ₹1,002.50 | CGST: 0.125% | SGST: 0.125% |
| 3% | Gold, silver, jewellery, platinum, and specific precious metal articles. | Base: ₹1,000 | Tax: ₹30.00 | Total: ₹1,030.00 | CGST: 1.5% | SGST: 1.5% |
| 5% | Packaged staples, edible cooking oil, tea, coffee, life-saving medicines, and railway transport. | Base: ₹1,000 | Tax: ₹50.00 | Total: ₹1,050.00 | CGST: 2.5% | SGST: 2.5% |
| 12% | Processed foods, pharmaceuticals, business class air travel, and select apparel. | Base: ₹1,000 | Tax: ₹120.00 | Total: ₹1,120.00 | CGST: 6% | SGST: 6% |
| 18% | Standard capital equipment, industrial goods, telecom, IT services, consulting, and banking. | Base: ₹1,000 | Tax: ₹180.00 | Total: ₹1,180.00 | CGST: 9% | SGST: 9% |
| 28% | Luxury motor vehicles, aerated soft drinks, tobacco products, and high-end electronics. | Base: ₹1,000 | Tax: ₹280.00 | Total: ₹1,280.00 | CGST: 14% | SGST: 14% |
Answers to practical questions regarding GST computations and invoicing rules.
For Add GST mode, the calculator computes tax as (Base Amount × Rate) ÷ 100 and adds it to the base. For Remove GST mode, the calculator isolates the original pre-tax value using (Inclusive Amount × 100) ÷ (100 + Rate), ensuring exact mathematical rounding.
Use Add GST when preparing an invoice from a net quotation to find the final total payable. Use Remove GST when examining a consumer bill or retail sticker price to uncover the underlying base price and the embedded tax amount.
On intra-state transactions, the total GST percentage is apportioned equally: 50% as Central GST (CGST) and 50% as State GST (SGST). For instance, an 18% slab splits into 9% CGST and 9% SGST.
Integrated GST (IGST) applies whenever goods or services are supplied across state boundaries or imported. The full tax rate is collected under IGST by the central administration and allocated to the destination state.
Selecting the Custom rate option enables an input field where you can specify any valid percentage from 0% to 100%. The tool immediately computes the tax and updates all breakdown figures.
Yes, completely. Every calculation runs client-side in your browser. No financial figures, invoice amounts, or personal identifiers are collected, tracked, or sent across the network.
