Percentage formulas
Common uses
- Salary increase: new salary = current × (1 + raise %).
- Discount: price × (1 − discount %). A 30% discount on 250 = 175.
- Budget variance: (actual − budget) ÷ budget × 100.
- Margin vs markup: margin = profit ÷ price; markup = profit ÷ cost. A 25% markup is a 20% margin.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. 15% of 240 = 240 × 15 ÷ 100 = 36.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100. 36 is what % of 240? 36 ÷ 240 × 100 = 15%.
How do I calculate percentage change?
(New − Old) ÷ Old × 100. From 80 to 100 is +25%; from 100 to 80 is −20%. Note the asymmetry: the base is always the old value.
What is the difference between percentage points and percent?
If a rate rises from 5% to 7%, that is a rise of 2 percentage points but a 40% increase (2 ÷ 5). Interest rates and tax rates are usually quoted in points.
How do I add or subtract a percentage?
Multiply by (1 + p/100) to add or (1 − p/100) to subtract. Adding 20% to 50 = 50 × 1.2 = 60. Subtracting 20% from 60 = 48, not 50 — removing a percentage does not reverse adding it.
How do I reverse a percentage increase?
Divide by (1 + p/100). If a price including a 15% markup is 230, the original was 230 ÷ 1.15 = 200. This is the same logic as removing VAT.