Calculate percentages, increases, and decreases instantly.
Percentage calculations explained
A percentage is a number expressed as a part of 100. People use percentages for discounts, marks, interest rates, taxes, salary hikes and statistics. This calculator handles the three most common questions so you do not need to remember which formula to use.
The three common calculations
- What is X% of Y? Result = Y × X ÷ 100. Example: 15% of 2,400 = 2,400 × 15 ÷ 100 = 360.
- X is what percent of Y? Result = X ÷ Y × 100. Example: 45 out of 60 = 45 ÷ 60 × 100 = 75%.
- Percentage change = (New − Old) ÷ Old × 100. Example: salary rising from 40,000 to 46,000 is (46,000 − 40,000) ÷ 40,000 × 100 = 15% increase.
Common mistakes
- Percentage points are not percent. If an interest rate moves from 6% to 8%, it rose by 2 percentage points but by 33.3% in relative terms.
- Increases and decreases are not symmetric. A 20% drop followed by a 20% rise leaves you at 96% of the start, not 100%.
- Divide by the correct base. Percentage change is always measured against the old value.
Frequently asked questions
How do I calculate a percentage in my head?
Find 10% by moving the decimal one place, then build from it. For 15% of 2,400: 10% is 240, 5% is half of that (120), so 15% is 360.