GST / Tax Calculator

A price tag showing a pre-tax figure needs the final checkout amount worked out, or a receipt total needs to be broken down to see how much of it was actually tax — this calculator handles both directions of GST/sales tax math in one tool.

The difference between "add tax" and "remove tax" modes

Add tax is for when you have a base price and want to know the final amount after tax is applied — for example, a product priced at 1000 with 17% tax added comes to 1170. Remove tax is for the reverse situation: you have a final, tax-inclusive total (like a receipt total) and want to know how much of that was the base price versus the tax portion — critical because simply subtracting the tax percentage from the total gives the wrong answer (the correct method divides by 1 + tax rate, not by subtracting the percentage directly).

Where this comes up regularly

A small business owner pricing a product and needing to know the final customer-facing price after tax. A shopper checking a receipt to see the actual tax paid versus the item's base price for expense reporting. A freelancer calculating how much tax to add to an invoice total based on their local tax rate.

Frequently Asked Questions

Why can't I just subtract the tax percentage to reverse-calculate? Because tax is calculated on the base price, not the total — subtracting 17% directly from a tax-inclusive total overstates the tax removed; dividing by (1 + tax rate) is the mathematically correct way to back out the base price.

Does this work for any tax rate, not just GST? Yes — the same add/remove math applies to VAT, sales tax, or any percentage-based tax; just enter the applicable rate for your situation.

Is my financial data saved anywhere? No — the calculation runs entirely in your browser using JavaScript; nothing is stored or transmitted.