What GST means here
GST (Goods and Services Tax) is a value-added tax used in several countries, often at a standard rate such as 10% or 15%. Similar ideas apply to sales tax or VAT in other regions. Always confirm the rate and rules that apply to your situation.
Formulas
Add tax to a net (ex-tax) amount
Tax = Net × (Rate ÷ 100)
Gross = Net + Tax
Gross = Net × (1 + Rate ÷ 100)
Remove tax from a gross (tax-inclusive) amount
Net = Gross ÷ (1 + Rate ÷ 100)
Tax = Gross − Net
Examples (using 10% for illustration)
Add 10% GST to $200 net:
Tax = 200 × 0.10 = $20
Gross = 200 + 20 = $220
Remove 10% GST from $220 gross:
Net = 220 ÷ 1.10 = $200
Tax = 220 − 200 = $20
Using 18% (common illustrative rate in some regions) on $1,000 net:
Gross = 1000 × 1.18 = $1,180
Common mistakes
- Removing tax by subtracting Rate% of the gross amount instead of dividing by (1 + rate). For 10% GST, tax is not simply 10% of the gross figure.
- Applying the wrong rate, or ignoring exemptions and special rules.
- Treating calculator output as formal tax advice.
Disclaimer
Tax rules vary by country and product type. Calculator results are for general information only. Confirm obligations with official guidance or a qualified adviser.
Use the free GST tool:
Open GST Calculator