How GST works
Goods and Services Tax is a single indirect tax on the supply of goods and services in India. Sellers add GST to their price, collect it from buyers, and remit it to the government. Depending on the item, the rate is one of a few fixed slabs — most commonly 5%, 12%, 18% or 28%.
There are two everyday calculations: adding GST (you know the base price and need the final price) and removing GST (you have the final price and need to know how much tax is inside it). This tool does both.
The formulas
Add GST (amount is exclusive of tax):
GST = Amount × rate ÷ 100 and Total = Amount + GST
Remove GST (amount is inclusive of tax):
Base = Amount ÷ (1 + rate ÷ 100) and GST = Amount − Base
For an intra-state sale, the GST is then split equally: CGST = SGST = GST ÷ 2.
Worked examples
Adding 18% GST to a base of ₹10,000: GST = 10,000 × 18% = ₹1,800, so the total is ₹11,800. The tax splits into ₹900 CGST + ₹900 SGST.
Removing 18% GST from an inclusive ₹11,800: Base = 11,800 ÷ 1.18 = ₹10,000, so the GST inside the price is ₹1,800. Again ₹900 CGST + ₹900 SGST.
The two are mirror images — useful when a customer quotes you an all-inclusive price and you need to know the taxable value for your books.
Practical tips
- Quote clearly. State whether a price is GST-inclusive or exclusive to avoid disputes.
- Use the right slab. Charging the wrong rate creates reconciliation headaches; check the HSN/SAC code for your product or service.
- Intra-state vs inter-state. The total GST is the same either way; only the split (CGST+SGST versus IGST) differs based on where the buyer and seller are located.
For tax on income rather than goods, see the income tax calculator.