GST Calculator (India)

GST (Goods and Services Tax) is India's single indirect tax on the supply of goods and services. It replaced a tangle of earlier taxes — central excise, service tax, VAT, octroi and several more — when it launched on 1 July 2017, folding them into one tax levied at every stage from factory to shop. Its defining feature is the input tax credit: a registered business pays GST on what it buys and claims a credit for that against the GST it collects on what it sells, so the tax never piles up on top of itself along the supply chain. GST is charged at four main rates depending on the item: 5%, 12%, 18% and 28% (plus 0% and 3% for a few special goods).

Two ways to use GST

1. Add GST to a price (exclusive price): if you sell at ₹10,000 plus 18% GST, the GST is ₹10,000 × 18% = ₹1,800 and the customer pays ₹11,800.

GST = amount × rate / 100
Total = amount + GST

2. Extract GST from an inclusive price: if the customer pays ₹11,800 and that price already includes 18% GST, the base is ₹11,800 / 1.18 = ₹10,000 and the GST is ₹1,800.

Base = amount / (1 + rate / 100)
GST = amount − base

The second mode matters every time a shopkeeper says "₹11,800, GST included" and you need to know the pre-tax amount — for your own accounts, for a refund, or to check that the tax on the invoice matches the rate you were promised.

Which rate applies?

• 5% — most packaged food, medicines, domestic LPG, rail/air economy
• 12% — computers, processed food, business-class air travel
• 18% — most services, telecom, restaurants, packaged consumer goods
• 28% — luxury goods, cars, tobacco, aerated drinks (some also attract a cess)

When in doubt, ask your supplier or check the GST council rate schedule — the rate really depends on the specific HSN/SAC code of your item. Goods are classified under HSN codes, services under SAC codes, and a genuinely surprising number of disputes come down to which code a product actually falls under.

Reading a GST invoice

A correct tax invoice shows four amounts: the base price, the CGST (central GST), the SGST (state GST) and the total. For intra-state sales, CGST and SGST are usually two equal halves that add up to the full rate (18% becomes 9% + 9%); for inter-state sales, a single IGST at the full rate applies. If you are a registered business, these printed amounts are what you claim as input credit — which is why estimates should never replace the figures on the actual invoice.

Who does the paying

• Consumers pay GST embedded in retail prices, which are normally GST-inclusive.
• Businesses above the registration threshold collect GST on sales and remit the difference between that and the input credit they claim — only the value added at each stage is effectively taxed.
• Small suppliers can use the composition scheme, paying GST at a flat low rate on turnover instead of performing full input-credit accounting.

Common questions people actually ask

• "Why did my ₹10,000 bill suddenly say ₹11,800?" — because the advertised price was GST-exclusive and the tax was added on top.
• "My vendor said 5%, but I was charged 12%." — check whether the item's HSN code was correctly applied; misclassification is common for items that could sit in more than one category.
• "Can I avoid GST by buying without an invoice?" — no invoice means no input credit for a business buyer, and liable transactions still attract tax.