GST Calculator

Calculate Goods and Services Tax

GST is added to goods and services in many countries, and calculating it, or extracting it from an inclusive price, is routine. This calculator adds GST to a net amount or removes it from a gross amount at your rate.

Why the reverse calculation matters

Adding GST is straightforward, but finding the GST already inside a tax-inclusive price is where errors creep in, because the tax was added to the base, not the total. Taking the percentage off the gross overstates the base; the correct reverse is to divide the gross by one plus the rate to find the base, with the remainder being the GST. This matters for invoicing and accounting, where separating the tax from an inclusive figure has to be exact, since the components are reported separately.

A planning estimate

This is an estimate for planning from the figures you enter, not financial or business advice. Real outcomes depend on factors beyond any single calculation, so treat the result as a guide. The calculation runs entirely in your browser, so your figures are never uploaded and stay on your own machine, which matters for business numbers you would not want to share.

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