Percentage formulas
- X % of a number: number × X ÷ 100. Example: 20 % of 150 = 150 × 20 ÷ 100 = 30.
- What percent is X of Y: X ÷ Y × 100. Example: 30 of 120 = 25 %.
- Percentage change: (new − old) ÷ old × 100. From 80 to 100 is +25 %; from 100 to 80 is −20 %.
- Price after discount: price × (1 − discount ÷ 100). €59.99 with 30 % off = €41.99.
- Increase by a percentage: amount × (1 + percent ÷ 100). €1,000 + 5 % = €1,050.
- Reverse percentage: amount ÷ percent × 100. If 45 is 15 %, the whole is 300.
Common mistakes
A rise and a fall of the same percentage do not cancel out. A price that rises 20 % and then falls 20 % ends 4 % lower than it started (100 → 120 → 96).
Percentage points are not percent. If an interest rate goes from 3 % to 4 %, it rose by one percentage point, but by 33 % in relative terms.
Removing VAT: to get the net price from a gross price with 25 % VAT, divide by 1.25, do not subtract 25 %. Use the VAT calculator.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15 % of 80 is 80 × 15 ÷ 100 = 12.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. From 50 to 65 is (65 − 50) ÷ 50 × 100 = 30 %.
How do I find the original price before a discount?
Divide the discounted price by (1 − discount ÷ 100). A €70 price after 30 % off was originally €70 ÷ 0.7 = €100.
What is the difference between percent and percentage points?
Percentage points measure the absolute difference between two percentages (3 % to 4 % is one point); percent measures the relative change (33 %).
Updated: November 2026 · Supremio Digital, Zagreb
