Useful percentage formulas
- X% of Y = X × Y ÷ 100
- Percentage change = (new − old) ÷ old × 100
- Profit margin = (price − cost) ÷ price × 100
- Markup = (price − cost) ÷ cost × 100
Margin and markup are often confused: a 25% markup on cost gives only a 20% margin on price. For tax on a price, use our GST calculator.
Frequently Asked Questions
What is the difference between margin and markup?
Margin is profit as a percentage of the selling price; markup is profit as a percentage of cost.
How do I reverse a percentage increase?
Divide the new value by (1 + rate/100). For example, 118 ÷ 1.18 = 100.
This calculator gives an estimate based on the rules shown above. Rates and limits change through budgets and notifications – confirm with a professional before you file or pay.