GST Calculator

About the GST Calculator

GST catches out business owners and shoppers alike — add it wrong on an invoice and you either short-change yourself or overcharge a customer. The rules are simple once you know them: you add tax to a base price, but you divide to remove it from a GST-inclusive total.

This GST Calculator adds or removes GST at 5%, 12%, 18% or 28% (or any rate) and splits the tax into CGST and SGST, so every invoice you produce is correct.

How to use the GST Calculator

1. Enter the amount (base or GST-inclusive).
2. Choose the GST rate (5%, 12%, 18%, 28% or custom).
3. Select whether to add or remove GST.
4. See the base, GST, CGST/SGST split and total.

Key features of the GST Calculator

• Adds or removes GST at any rate
• Splits GST into CGST and SGST
• Correct reverse-GST calculation
• Produces accurate invoice figures
• Runs privately in your browser

How the GST Calculator works

This calculator uses the established mathematical formulas that banks, lenders and financial institutions rely on — for interest, amortization, EMI, compounding, tax and investment growth. Where local rules apply (such as tax bands or GST/VAT rates), the tool follows the relevant published structure, and figures can be expressed in the currency you work in.

Every calculation runs in your browser, so the financial figures you enter stay completely private.

Tips & best practices

• To remove GST from an inclusive price, divide by one plus the rate — never simply subtract the percentage.
• For a sale within a state, GST splits equally into CGST and SGST; inter-state sales use a single IGST at the full rate.
• Always state on an invoice whether a price includes GST so customers and suppliers are clear.

Standards & accuracy

Uses the same standard financial formulas as banks and lenders, with support for multiple currencies and international tax rules.

Disclaimer: results are estimates for general information only and are not financial advice. Rates, fees and tax rules change and vary by provider and jurisdiction. Confirm figures with your bank, lender or a qualified financial professional before making decisions.

Who uses the GST Calculator?

• Preparing GST-compliant invoices
• Working out the base price from a GST total
• Splitting tax into CGST and SGST
• Everyday business and shopping maths

Privacy & security

The GST Calculator runs entirely inside your web browser. Your data — whether that is a file, figures or text — is processed on your own device and is never uploaded to a server, stored or shared. There is no signup and no account, so you can use it as often as you like while keeping full control of your information. This makes it a safe choice even for confidential and sensitive work.

Why choose Toolinza?

• 100% free — no hidden charges, watermarks or usage caps.
• Private & secure — your data stays on your device.
• Standards-compliant — accurate results suitable for the UK, USA, Canada, Australia, EU, India, Pakistan, the Middle East and worldwide.
• Works everywhere — desktop, tablet and mobile.

Frequently asked questions