GST Tax Calculator
A goods and services tax (GST) calculator with two directions. Add GST to a pre-tax amount to find the tax and the gross total, or Subtract GST from a GST-inclusive price to recover the net amount and the tax already inside it. Pick a country for a typical GST rate or type any rate you need — everything is computed in your browser.
Picks a typical GST rate; choose Other to enter your own.
Pre-tax net for Add GST · GST-inclusive total for Subtract GST.
Set by the country list; edit freely.
Pick a country or set the rate
Choose Australia, Canada, Hong Kong, India, Malaysia, New Zealand, or Singapore to load a typical GST rate, or select other country and type your own rate in percent.
Enter the amount
Type the amount in dollars. For Add GST this is the pre-tax net amount; for Subtract GST it is the GST-inclusive total you already paid.
Add or Subtract GST
Press Add GST to gross a net amount up, or Subtract GST to strip tax out of a gross amount. Read off the net amount, GST rate, GST amount, and gross amount, then Reset to start over.
How the math works
- What formulas does this calculator use?
- GST amount = GST rate (%) × net amount, and gross amount = net amount × (100% + GST rate %). Subtract GST is the inverse: net amount = gross amount × 100 ÷ (100 + GST rate), and the GST inside the total is the gross amount minus the net amount.
- Worked example
- Net amount $100 at a 10% GST rate: GST amount = 10% × $100 = $10, and gross amount = $100 × (100% + 10%) = $110. Running Subtract GST on the $110 total at 10% recovers exactly $100 net and $10 of GST.
- Where do the country rates come from?
- The country list loads commonly used standard GST rates for quick starting (for example Australia 10%, India 18%, New Zealand 15%, Hong Kong 0%). Tax rates change over time and vary by region and good, so check your local authority and edit the rate freely — choosing other country keeps whatever rate you type.
- When do I use Subtract GST instead of Add GST?
- Use Add GST when you hold a pre-tax price and need the tax-inclusive total (invoicing a customer). Use Subtract GST when a receipt already shows the GST-inclusive price and you need to recover the net amount and the tax portion (claiming input tax credits, splitting a final bill).
- Can the rate be 0%?
- Yes. A 0% rate (like Hong Kong’s) is valid: the GST amount is $0 and the gross amount equals the net amount. Negative amounts and negative rates are rejected, and money outputs are rounded to cents.
Privacy: every calculation runs in your browser tab — no value you type is sent anywhere. This tool is for estimation, not tax advice.