GST Calculator
Add GST to a price or strip it back out of one that already includes it, at 5%, 12%, 18%, 28% or any rate you type. The remove mode is the one people get wrong by hand — you cannot simply subtract 18% from a GST-inclusive price and arrive at the original amount.
This is a calculation aid, not tax advice. GST rates and exemptions vary by goods and service category — confirm the applicable rate for your specific case with a tax professional or the GST portal.
How to calculate GST
- Enter the amount.
- Pick a GST rate, or type a custom one.
- Choose “Add GST” or “Remove GST” and read the result.
When you'd use this
- Writing an invoice — Adding the right GST to a quoted price before billing a customer.
- Checking a bill — Confirming the tax on a restaurant or shop receipt is what it should be.
- Working backwards from a price — Finding the pre-tax value of an inclusive price for your own accounts.
- Quoting to a customer — Showing a price with and without tax so there is no confusion later.
Good to know
- Adding and removing are different sums — Adding 18% multiplies by 1.18. Removing it divides by 1.18 — subtracting 18% from the inclusive price gives the wrong answer, and by a noticeable margin.
- Custom rates are supported — The four presets cover the common slabs, but any rate can be typed in, including 0 and fractional rates.
- This is India's GST system — The preset rates are the Indian slabs. The arithmetic itself works for any percentage-based sales tax anywhere.
- It does not split CGST and SGST — The tool shows the total tax. How it divides between central and state components depends on the transaction and is a matter for your accounting.
Frequently asked questions
What's the difference between Add and Remove?
“Add GST” treats your amount as the base price and adds GST on top. “Remove GST” treats your amount as already including GST and works backward to find the base price.
Which GST rate should I use?
Use whichever rate applies to your goods or service under India's GST slabs — 5%, 12%, 18% or 28% are the most common, or enter a custom rate.
How do I remove GST from a price that already includes it?
Choose Remove GST and enter the inclusive amount. The tool divides by 1 plus the rate — for 18% that means dividing by 1.18, not subtracting 18%.
Why can't I just subtract 18% to get the original price?
Because the 18% was calculated on the smaller pre-tax figure, not on the final price. Subtracting 18% from an inclusive price of 118 gives 96.76, when the correct answer is 100.
Can I use a rate that isn't one of the presets?
Yes. Type any figure into the custom rate box, including 0 or a decimal rate, and it takes precedence over the preset buttons.