What is GST?
Goods and Services Tax (GST) is India's single indirect tax on the supply of goods and services. Common rates are 5%, 12%, 18% and 28%. For sales within a state, GST is split equally into CGST (central) and SGST (state); for inter-state sales it is charged as IGST at the same total rate.
Add GST vs Remove GST
- Add GST — you have the base price and want the final price. GST = base × rate. Use this to bill a customer.
- Remove GST — you have the final (inclusive) price and want the base. Base = total ÷ (1 + rate). Use this to find the pre-tax value of a receipt.
Formula
Worked example
Adding GST. A base amount of ₹10,000 at 18% carries ₹1,800 of tax, so the invoice total is ₹11,800. Within one state that ₹1,800 appears as two lines of ₹900 each, CGST and SGST; across states it appears as a single IGST line of ₹1,800. The customer pays the same either way — the split only decides which government receives it.
Removing GST. From an inclusive ₹11,800 at 18%, the base is 11,800 × 100 ÷ 118 = ₹10,000 and the tax inside it is ₹1,800. Subtracting 18% from ₹11,800 gives ₹9,676, which is wrong by ₹324 — the percentage was never applied to ₹11,800 in the first place.
Is the price inclusive or exclusive?
Getting this wrong is the single most common GST error, and it usually surfaces only when an invoice is disputed.
- Retail prices in India are inclusive. The MRP printed on a pack already contains the tax, so no GST is added at the till. Use Remove GST to find what the item cost before tax.
- B2B quotations are usually exclusive and say "plus GST". Use Add GST to reach the amount that will actually be invoiced.
- Say which one you mean in writing. A quote for ₹1,00,000 means ₹1,18,000 or ₹1,00,000 depending on one missing word.
- Check before you compare quotes. An exclusive quote will always look cheaper than an inclusive one for the same work.
GST rates and rules are set by the GST Council and are revised from time to time. Confirm the rate that currently applies to your goods or service before relying on any figure — this is a calculator, not tax advice.
Frequently asked questions
How are CGST and SGST calculated?
For a within-state sale, the total GST is split equally — e.g. 18% becomes 9% CGST + 9% SGST.
Can I use a custom rate?
Yes — type any rate in the custom box for special cases like 3% (gold) or 0.25%.
Why can I not just subtract the percentage to remove GST?
Because the percentage was applied to the smaller base amount, not to the inclusive total. Subtracting it from the total takes off too much. Divide by 100 plus the rate, then multiply by 100.
What is a reverse GST or inclusive price calculation?
It is the Remove GST mode here: working backwards from a price that already contains the tax to find the base value and the tax inside it. Retail prices in India are quoted inclusive, so this is the direction most people need.
Does the amount of GST change if the buyer is in another state?
No. The total is the same; only its composition changes. Within a state it is split into CGST and SGST, and between states it is charged as IGST at the full rate.