What is GST?
GST stands for Goods and Services Tax — a comprehensive, multi-stage, destination-based tax levied on every value addition in the supply chain. Introduced in India on 1 July 2017 under the GST Act, it replaced a web of central and state taxes including VAT, service tax, excise duty, and octroi.
GST is a consumption-based tax, meaning the tax revenue goes to the state where the goods or services are consumed, not where they are produced. It is designed to create a unified national market, eliminate cascading taxes (tax on tax), and simplify compliance for businesses across India.
How this GST calculator helps you
Whether you are a business owner preparing invoices, a freelancer determining your service fees, or a consumer checking the tax on a purchase, this calculator simplifies the process in the following ways:
GST slabs in India
India follows a four-tier GST rate structure designed to balance revenue needs with affordability for consumers. Essential goods are taxed at lower rates or exempt, while luxury and demerit goods attract the highest rate.
5% GST slab
This slab covers essential items of daily use. It includes packaged food items, footwear priced below ₹1,000, apparel below ₹1,000, cream milk, paneer, branded cereals, and transport services like railway and metro fares.
12% GST slab
The 12% slab applies to goods and services that are considered standard necessities. This includes processed food items, computers and accessories, mobile phones, umbrella, sewing machines, and business class air travel.
18% GST slab
The most common slab, 18% covers the majority of goods and services including IT and telecom services, restaurant bills, hotel rooms between ₹2,500 and ₹7,500, toothpaste, soap, and capital goods like industrial machinery.
28% GST slab
This is the highest slab reserved for luxury items and sin goods. It covers automobiles, tobacco products, aerated drinks, premium appliances, motorcycles above 350cc, and luxury hotel rooms above ₹7,500 per night. Some items in this slab also attract a separate cess.
Goods that are exempt from GST — meaning 0% tax — include fresh vegetables and fruits, milk, eggs, unbranded flour and rice, salt, and educational services. These items remain outside the GST net to protect basic necessities from taxation.
CGST vs SGST vs IGST
The division of GST into CGST, SGST, and IGST depends entirely on the nature of the transaction — specifically, whether the supply of goods or services takes place within the same state or across state borders.
Intra-state transactions (CGST + SGST)
When a seller and buyer are located in the same state, the transaction is intra-state. The total GST is split equally: half is collected as CGST (Central GST) by the central government, and half as SGST (State GST) by the state government. For example, at 18% GST, CGST is 9% and SGST is 9%. Both the central and state governments receive an equal share of the tax revenue.
Inter-state transactions (IGST)
When a seller and buyer are in different states, the transaction is inter-state. The full GST is collected as IGST (Integrated GST) by the central government. The central government then apportions the revenue to the destination state where the goods or services are consumed, ensuring that the consuming state receives the tax benefit.
The key principle is that the total GST percentage is identical in both cases — only the split changes. This design ensures a seamless flow of input tax credit across the supply chain, regardless of state boundaries.
GST calculation formula
The mathematics of GST calculation is straightforward and consistent across all slab rates. There are two primary scenarios depending on what information you start with:
Adding GST to a base price
If you know the taxable value (base price) and need to find the GST-inclusive total:
GST Amount = Base Price × (GST Rate / 100)
Total Amount = Base Price × (1 + GST Rate / 100)
Extracting GST from a total amount
If you have the GST-inclusive price and need to determine the base price and GST component:
Base Price = Total Amount / (1 + GST Rate / 100)
GST Amount = Total Amount - Base Price
CGST / SGST / IGST breakdown
For intra-state: CGST = SGST = GST Amount / 2. For inter-state: IGST = GST Amount (full amount).