How to Add and Remove GST: A Simple Guide

To add GST, multiply the net amount by the rate and divide by 100, then add it to the net; to remove GST from an inclusive price, divide the price by (1 + rate ÷ 100). A free browser calculator does both directions across the 5%, 12%, 18% and 28% slabs and shows net, tax and gross together.

GST math runs in two directions, and confusing them is a costly habit. Adding tax to a quote is one calculation; working out how much tax is buried inside a receipt total is another. This guide covers both, plus the CGST/SGST split that trips up new business owners.

Why a two-way GST calculator matters

Invoicing usually starts from a net amount and adds GST. But reconciling receipts, claiming input credit, or checking a price often means going the other way — extracting the tax already inside an inclusive figure. A calculator that handles both, with preset Indian slabs and a custom field, saves you from applying the wrong formula. It's designed for small-business owners raising invoices, freelancers quoting clients, accountants reverse-calculating tax, and shoppers curious what portion of a price is tax. Net, GST and gross are always shown side by side, and nothing you enter leaves your browser.

How to calculate GST in your browser

1. Choose the mode: Add GST for a tax-exclusive amount, or Remove GST for a tax-inclusive price.
2. Enter your amount.
3. Pick a preset rate (5%, 12%, 18% or 28%) or choose Custom and type any rate.
4. Read the net amount, GST amount and gross total instantly, with the CGST/SGST split shown.

Add GST vs remove GST: worked examples

The same rate produces different numbers depending on direction. Here's 18% GST both ways, so the distinction is clear.

Task	Formula	Example (18%)
Add GST to net	net × (1 + rate/100)	₹1,000 → ₹1,180 (₹180 tax)
Remove GST from gross	gross ÷ (1 + rate/100)	₹1,180 → ₹1,000 (₹180 tax)
Intra-state split	CGST + SGST, each rate/2	18% = 9% + 9%

Notice you can't just subtract 18% of the inclusive price to remove GST — that would over-deduct. Dividing by 1.18 is the correct reverse operation, and the tool applies it for you.

Key features and benefits

• Add-GST and remove-GST (inclusive) modes.
• Preset 5%, 12%, 18% and 28% slabs plus custom rates.
• Shows net, GST amount and gross together.
• CGST/SGST split shown for intra-state supplies.
• 100% private — nothing leaves your browser.
• Free, instant, no sign-up.

Try the GST Calculator now — it's free and runs entirely in your browser.

Frequently asked questions

How do I calculate GST on an amount?

Multiply the net amount by the GST rate and divide by 100, then add it to the net. For ₹1,000 at 18% the tax is ₹180, making the total ₹1,180. The Add GST mode does this automatically.

How do I remove GST from a total price?

Divide the inclusive price by (1 + rate ÷ 100). A ₹1,180 price at 18% contains a net of 1,180 ÷ 1.18 = ₹1,000 and ₹180 of tax. Use Remove GST mode for the exact split.

What are the GST slab rates in India?

The main slabs are 5%, 12%, 18% and 28%, with 18% applying to most services. Some items are zero-rated or taxed at special rates like 0.25% or 3% for precious stones and metals — use the custom field for those.

What's the difference between CGST, SGST and IGST?

For sales within a state, GST splits equally into CGST (central) and SGST (state), so 18% becomes 9% + 9%. For inter-state sales the full amount is charged as IGST. The tool shows the CGST/SGST split for you.

Is GST calculated on the discounted price?

Yes. GST is normally charged on the transaction value after any discount shown on the invoice. Apply the discount first, then add GST on the reduced amount.

Related free tools

• VAT Calculator — add or extract VAT from a price.
• Percentage Calculator — percent of, reverse and change.
• Discount Calculator — sale price and amount saved.
• EMI Calculator — monthly loan repayments.

Built by ByteVancer

ByteTools is a free product of ByteVancer, a software and web development studio that builds web apps, SaaS platforms and custom software for businesses. If your business needs custom invoicing, billing or accounting software, explore ByteVancer's services and get in touch to build it.