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GST Calculator

Quickly add GST to a price or extract GST from a GST-inclusive amount. Supports common GST rates and custom rates. Instantly see the GST amount and the final price.

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GST Formulas

Adding GST
GST Amount = Amount × Rate ÷ 100
Final Price = Amount + GST Amount
Removing GST
GST Amount = Price × Rate ÷ (100 + Rate)
Original Price = Price − GST Amount

How to Use the GST Calculator

  1. 1
    Choose a Mode
    Select "Add GST" to calculate the price including GST, or "Remove GST" to extract GST from an inclusive price.
  2. 2
    Enter the Amount
    Type the original price (Add mode) or the GST-inclusive price (Remove mode).
  3. 3
    Select the GST Rate
    Choose a common rate from the dropdown or select "Custom" to enter your own rate.
  4. 4
    Read the Breakdown
    The calculator instantly shows the original price, GST amount, and the final price with a full breakdown.

Example Calculations

Adding 18% GST to $1,000:

GST Amount = $1,000 × 18 ÷ 100 = $180
Final Price = $1,000 + $180 = $1,180

Removing 18% GST from $1,180:

GST Amount = $1,180 × 18 ÷ (100 + 18) = $180
Original Price = $1,180 − $180 = $1,000

Frequently Asked Questions

GST (Goods and Services Tax) is a value-added tax levied on most goods and services sold domestically. It is collected at each stage of the supply chain and is common in countries like Australia, India, Canada, Singapore, and New Zealand.

Multiply the original price by the GST rate divided by 100. For example, 10% GST on $500: GST = $500 × 10/100 = $50. The GST-inclusive price is $550.

Use the formula: GST Amount = Inclusive Price × Rate ÷ (100 + Rate). For 10% GST on $550: GST = $550 × 10 ÷ 110 = $50. The original price is $500.

When removing GST from an inclusive price, the base price is a smaller proportion of the total. Dividing by (100 + Rate) correctly accounts for this. Simply multiplying the inclusive price by the rate would give an incorrect result.

Australia uses 10%; New Zealand 15%; India has multi-rate slabs (5%, 12%, 18%, 28%); Canada uses 5% federal GST; Singapore 9%. Always check local regulations as rates change over time.

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