What is the GST Calculator?
Goods and Services Tax (GST) is a value-added consumption tax applied in many countries such as Australia, India, New Zealand, Canada and Singapore. This calculator works for any GST rate, letting you either add GST to a tax-exclusive (net) price or remove GST from a tax-inclusive (gross) price. It returns the net amount, the GST amount and the gross total in one step.
How to use it
Choose a calculation type. Select Add GST if your figure does not yet include tax, or Remove GST if your figure already includes tax. Enter the amount and the GST rate (for example 10 for Australia, 15 for New Zealand, or 18 for many Indian goods). The calculator instantly breaks the figure into net, GST and gross components.
The formula explained
When adding GST, the tax is simply a percentage of the net price: \( \text{GST} = \text{Net} \times \text{Rate} \), and the total is \( \text{Net} \times (1 + \text{Rate}) \). When removing GST from a gross figure, you reverse this: because the gross already equals \( \text{Net} \times (1 + \text{Rate}) \), the net is recovered with \( \text{Net} = \text{Gross} \div (1 + \text{Rate}) \) and the GST is the difference, \( \text{Gross} - \text{Net} \). The rate entered as a percentage is divided by 100 before use.
$$\begin{gathered} \text{GST} = \text{Amount} \times \frac{\text{Rate}}{100} \\[1em] \text{Gross} = \text{Amount} + \text{GST} \end{gathered}$$
Worked example
Suppose a product costs $100 net with a 10% GST rate. GST = $$100 \times 0.10 = \$10$$ so the total is $110. Now reverse it: a gross price of $110 at 10% gives Net = $$110 \div 1.10 = \$100$$ and GST = $$110 - 100 = \$10$$ — the figures match.
FAQ
What GST rate should I use? Use the rate that applies in your country or to your product category. The calculator does not assume a default rate.
Is the price net or gross? Net (or "exclusive") means before tax; gross (or "inclusive") means tax is already included. Pick the matching mode.
Does this work for VAT or sales tax? Yes. The maths is identical for any percentage-based VAT or sales tax — just enter the relevant rate.
