ConverterHub

GST Calculator

Add or remove GST from any amount.

How it is calculated

GST is a percentage added to the net price. In add mode the tool computes GST = amount × rate / 100 and gross = amount + GST. In remove mode the amount is treated as a tax-inclusive price, so net = amount ÷ (1 + rate / 100) and GST = amount − net. The rate is a percentage that you enter, as the standard GST or VAT rate differs from country to country and by product category. Results show GST, gross price and net price as money amounts with two decimals. A negative rate is not accepted.

Worked example

A shelf price of 118 includes 18% GST, so you use remove mode. Net price: 118 / 1.18 = 100.00. GST: 118 − 100 = $18.00. Gross stays $118.00. Notice that the tax is 18 and not 18% of 118, which would be 21.24. That is the typical mistake of taking the percentage off the gross amount.

Try this example →

Common mistakes

  • Subtracting 18% from the gross amount instead of dividing by 1.18; that removes too much.
  • Choosing add mode for a price that already includes GST, which taxes it twice.
  • Entering the rate as 0.18 instead of 18.
  • Using one rate for all items, when a country may apply reduced or zero rates to some goods.

About this calculator

This calculator adds or removes Goods and Services Tax from an amount: adding it multiplies the base price by (1 + GST rate), while removing it divides a GST-inclusive price by (1 + GST rate) to recover the pre-tax amount — the same reverse-tax logic used in countries like Australia, New Zealand, India, Canada, and Singapore, each with their own standard GST rate.

Business owners use it to price products correctly and issue GST-compliant invoices, accountants use it to reconcile GST-inclusive receipts back to net sales figures for tax filings, and shoppers use it to check exactly how much tax is baked into a listed price. The calculator handles both directions in one place, since "add GST" and "remove GST" are two different formulas that are easy to mix up.

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