GST Calculator
Add or remove GST from an amount at any tax rate, instantly.
Add GST to a pre-tax amount or remove it from a tax-inclusive price, at any rate — 5%, 12%, 18%, 28%, or a custom rate. Get the net amount, GST amount, and gross amount all at once, with worked examples for both directions.
How to use GST Calculator
- 1Enter your input for gst calculator.
- 2Review the result on this page.
- 3Download or copy your result.
Add vs. remove GST — worked examples
Adding GST starts from a pre-tax price and works forward: a ₹1,000 item at 18% GST has a tax amount of 1,000 × 18 ÷ 100 = ₹180, making the final price ₹1,180. Removing GST does the reverse — starting from a tax-inclusive price and working backward to find the original amount: a ₹1,180 tax-inclusive price at 18% GST has an original (pre-tax) amount of 1,180 ÷ 1.18 = ₹1,000, meaning ₹180 of that ₹1,180 was tax.
A common mistake is subtracting the percentage directly from a tax-inclusive amount (1,180 − 18% = ₹967.60) instead of dividing by (1 + rate) — that gives the wrong answer, because 18% of the tax-inclusive amount isn't the same as 18% of the original pre-tax amount. This calculator handles that division correctly for you.
Understanding GST slabs
GST rates vary by category of goods or service, not by a single flat rate across everything — common slabs are 5% (essential goods), 12% and 18% (standard goods and most services), and 28% (luxury and sin goods). Which rate applies depends entirely on what's being sold, so this calculator lets you enter any rate rather than assuming a fixed one, whether you're calculating for an invoice, a purchase, or checking a receipt.
Frequently Asked Questions
What's the difference between adding and removing GST?
"Add GST" takes a pre-tax amount and shows the tax and final price. "Remove GST" takes a tax-inclusive amount and works backward to show the original pre-tax amount.
Which GST rate should I use?
Use whichever slab applies to your goods or service (common slabs are 5%, 12%, 18%, and 28%) — you can also enter any custom rate.
Is this tool really free?
Yes, GST Calculator is completely free to use — no sign-up, no hidden charges.