Percentage formulas
X% of a number = number × X ÷ 100. Example: 15% of 200 = 30.
A as a percent of B = A ÷ B × 100. Example: 45 of 60 = 75%.
Percentage change = (new − old) ÷ old × 100. Example: a salary going from 8,000 to 9,000 is a 12.5% raise.
Margin vs. markup
If you buy at 80 and sell at 100, the profit is 20. Markup on cost = 20 ÷ 80 = 25%, while margin on selling price = 20 ÷ 100 = 20%. Mixing them up is one of the most common pricing mistakes.
FAQ
How do I work out a discount?
Multiply the price by the discount percent and divide by 100 to get the amount off, then subtract it from the price. Example: 30% off 350 = 105 off, so you pay 245.
What is the difference between margin and markup?
Markup is measured against cost, margin against the selling price. For the same product, markup is always higher than margin.
Are 20% and then 10% off the same as 30% off?
No. The second discount applies to the already-reduced price, so the total is only 28%: 100 → 80 → 72.
Check whether prices include VAT before you calculate profit.