GST Calculator
Add or extract GST at 5%, 12%, 18% or 28% - with CGST/SGST split.
How to use
- Choose add-GST (exclusive) or extract-GST (inclusive) mode.
- Enter the amount and tap a GST slab.
- Read base, GST amount, total and the CGST/SGST split.
Frequently asked questions
How does reverse GST work?
For an inclusive total T at rate g, the base is T ÷ (1 + g). The tool does this automatically in extract mode.
What are CGST and SGST?
Within a state, GST splits equally into central (CGST) and state (SGST) halves - shown separately for invoicing.
Add or remove GST in one step
GST calculations run in both directions, and this tool does both: add GST to a base (exclusive) price to find the total a customer pays, or extract GST from a total (inclusive) price to find the pre-tax amount and the tax within it. Enter the amount, pick the rate, and get the base, the GST and the total together - with the tax split into CGST and SGST halves for Indian invoicing.
Exclusive vs. inclusive, and why it confuses
The classic mistake is running the calculation the wrong way. If a price is quoted before tax, you add GST: ₹1,000 plus 18% is ₹180 tax and ₹1,180 total. If a price already includes tax, you can't just subtract 18% - you divide by 1.18 to recover the base (₹1,180 inclusive gives ₹1,000 base and ₹180 tax). Getting this backwards is one of the most common invoicing errors, and the inclusive/exclusive toggle here removes the guesswork.
The common Indian GST slabs - 5%, 12%, 18% and 28% - are one tap each, and the tax is shown as CGST + SGST for intra-state billing.
For invoices and quick checks
Small businesses use it to price goods and prepare invoices with the correct tax breakdown; shoppers use it to see how much of a price is actually tax. The same inclusive/exclusive logic applies to value-added taxes worldwide - our VAT Calculator covers European-style rates and our Sales Tax Calculator handles US state and local rates. For the discount that often comes before tax, the Discount Calculator pairs naturally with this one.