GST Calculator

What the GST Calculator does

The GST Calculator adds GST to a base amount or removes GST from a GST-inclusive amount, at any of the standard Indian tax slabs (5%, 12%, 18%, 28%) or a custom rate you specify, giving you both the tax amount and the final total.

How to use it

1. Choose the calculation type: add GST to an amount, or remove GST from an amount.
2. Enter the amount.
3. Enter or select the GST rate, then click Calculate GST.

Common uses

• Working out the GST-inclusive price to charge a customer from a base price.
• Reverse-calculating the base price and tax component from a GST-inclusive invoice total.
• Checking a vendor's invoice correctly applied the GST rate for a product or service category.
• Estimating tax liability on a sale before generating a formal invoice.
• Comparing final cost across the different GST slabs for budgeting purposes.

Good to know

"Add GST" and "Remove GST" are not simple inverses of each other done casually — removing 18% from a GST-inclusive amount doesn't mean subtracting 18% of the total, since the tax was originally calculated on the pre-tax base, not the final amount; the calculator handles this distinction correctly using the proper reverse formula, which is worth knowing if you're ever checking the math by hand.

GST slabs in India are assigned by product and service category rather than being a single flat rate, which means the correct rate to apply depends on correctly classifying what's being sold — an error here is one of the more common sources of invoicing mistakes for small businesses. When in doubt about which slab applies to a specific good or service, checking the current official GST rate schedule is worth the extra step before finalizing an invoice.