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GST Calculator

Calculate Goods and Services Tax amounts with inclusive/exclusive pricing for Australia, India, Canada, and other GST countries.

Tested tool guide Tested browser tools Checked August 16, 2026

What GST Calculator does, with a checked example

A GST price can be either a pre-tax amount waiting for tax or a tax-inclusive total that already contains it. GST Calculator handles both interpretations for Australia, India, Canada, and other GST jurisdictions: enter an amount, use the applicable percentage, and identify whether GST is included. It reports the tax portion and the corresponding before-tax and after-tax prices. The common mistake is multiplying an inclusive total directly by the stated rate. That overstates the embedded GST because the rate applies to the price before GST, not the already-taxed total.

Worked example

A concrete input and expected output from the current implementation.

Input

Amount: 110.00
GST rate: 10%
Pricing: GST-inclusive

Expected output

GST amount: 10.00
Price excluding GST: 100.00
Price including GST: 110.00

The embedded GST is 110.00 x 10 / 110 = 10.00. Subtracting 10.00 from the inclusive price leaves the 100.00 pre-tax amount.

How the result is produced

1

Adding GST

With GST-exclusive pricing, the entered amount is the base. The tax is the base multiplied by the rate and divided by 100, and the inclusive total is the base plus that tax. For 100.00 at 10%, the tax is 10.00 and the total is 110.00. Use this direction when a quote or line item is stated before GST.

2

Extracting included GST

With GST-inclusive pricing, the entered amount is the final total. The embedded tax is the total multiplied by the rate and divided by 100 plus the rate, not simply the total multiplied by the percentage. The exclusive amount is the final total minus the embedded tax. This calculation keeps the recovered base and GST equal to the original inclusive amount.

Good uses

  • Separating GST from a tax-inclusive receipt before recording revenue and the tax portion in bookkeeping.
  • Adding GST to a tax-exclusive quote or invoice line before giving a customer the payable total.
  • Comparing an advertised GST-inclusive price with a supplier price quoted before GST at the same selected rate.

Limits and checks

  • The calculator performs arithmetic after a rate is chosen. It does not decide whether a sale is taxable, exempt, zero-rated, or outside the relevant GST system.
  • Australia, India, and Canada do not have interchangeable indirect-tax structures. Confirm the jurisdiction and rate for the particular supply; a country name alone may not determine the treatment.
  • Currency rounding can make line-by-line invoice totals differ by a cent from GST calculated once on the invoice total. Reconcile the result against the document's own rounding method.

Common questions

Can I remove 10% GST by subtracting 10% from an inclusive price?

No. If 110.00 already includes GST at 10%, subtracting 11.00 would incorrectly leave 99.00. Divide the inclusive price by 1.10, or use the calculator's inclusive setting. The correct base is 100.00 and the embedded GST is 10.00. In general, divide by 1 plus the decimal tax rate to recover the base.

Does choosing a country prove that the GST rate and treatment are correct?

No. Applicable rates and classifications can depend on the jurisdiction, type of goods or services, place of supply, customer, and transaction date. Some systems also distinguish GST, HST, or separate provincial and state taxes. Use the calculator to check the price arithmetic after confirming the applicable treatment through current official guidance or a qualified adviser.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

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