GST Calculator
Add or extract GST from an amount using the rate you enter. Review the formula and assumptions before using the result.
Your input never leaves your device.
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Everything runs 100% locally in your browser. No files are uploaded to any server.
Formula
Tax-exclusive: GST = amount × rate ÷ 100. Tax-inclusive: base = amount ÷ (1 + rate ÷ 100); GST = amount − base.
Worked example
At 18%, 1,000 before tax becomes 1,180 including GST. Entering 1,180 with the inclusive option recovers a 1,000 base and 180 GST.
What the result means
Add or extract tax using a rate you supply. The tool does not determine local exemptions, registration requirements, input-tax credits, or invoice compliance.
How to Use GST Calculator
Enter the requested values
Provide the inputs for this gst calculator. Use consistent units where applicable.
Read the total including entered gst
The result recalculates as you edit the inputs.
Check the gst calculator assumptions
Use the gst calculator formula and notes below to understand what is—and is not—included.
Key Features & Benefits
Formula and worked example
At 18%, 1,000 before tax becomes 1,180 including GST. Entering 1,180 with the inclusive option recovers a 1,000 base and 180 GST.
Clear scope
Add or extract tax using a rate you supply. The tool does not determine local exemptions, registration requirements, input-tax credits, or invoice compliance.
Frequently Asked Questions
Can I extract GST from an inclusive price?
Yes. Select that the entered amount already includes tax.
Does selecting a currency choose the tax rate?
No. Currency changes display only; enter the verified rate applicable to your transaction.
Key terms
- gst calculator
- Add or extract tax using a rate you supply. The tool does not determine local exemptions, registration requirements, input-tax credits, or invoice compliance.