Tip: calculate first — your result is included when you share.
How to Use the GST Calculator
Goods and Services Tax is charged as a percentage of the price before tax. Choose Add GST if your amount is before tax, or Remove GST if the price already includes tax, then enter the amount, the rate and whether the supply is within a state or between states. Press Calculate GST for the base amount, the GST and the CGST + SGST or IGST split.
The insight most people miss is on the remove side: you cannot just subtract the rate from a tax-inclusive price. Removing 18% GST from Rs. 1,180 means dividing by 1.18 to get a base of Rs. 1,000 and GST of Rs. 180 — subtracting 18% of Rs. 1,180 would wrongly give Rs. 212.40. Division, not subtraction, is the whole trick.
A caveat: this is a one-amount calculator, not a filing tool. It does not look up your item's rate, does not include compensation cess on some goods, and does not cover input tax credit or composition-scheme rules. Rates also change, so always confirm the rate that currently applies to your item before invoicing.
For everyday price math without tax, try our Percentage Calculator, and if you bill clients, our Invoice Generator can turn your figures into a proper bill.
Frequently Asked Questions
How do I add GST to a price?
GST = price x rate / 100, and total = price + GST. For example, adding 18% GST to Rs. 10,000 gives Rs. 1,800 GST and a total of Rs. 11,800.
How do I remove GST from a tax-inclusive price?
Divide the total by (1 + rate/100). For example, Rs. 1,180 at 18% gives a base price of Rs. 1,180 / 1.18 = Rs. 1,000, so the GST inside it is Rs. 180. You cannot just subtract 18% of the total.
When is it CGST + SGST and when is it IGST?
For a supply within the same state, GST is split equally into CGST (central share) and SGST (state share). For a supply between states, the whole amount is charged as IGST instead.
What GST rate should I enter?
Enter the rate that applies to your item or service. Rates vary by item and are revised from time to time, so check the current notification for your product or service — this calculator does not look up rates for you.
Does this calculator handle cess or input tax credit?
No. It calculates GST on one amount only. Compensation cess on some items, input tax credit, and composition-scheme rules are not included — for filing, confirm with a tax professional.
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