Percentage Calculator
Three common percentage calculations in one tool: percent of a number, what percent one number is of another, and percentage change.
How this calculator works
- Choose which type of percentage question you're answering.
- Enter the two numbers involved.
- The calculator applies the right formula for that mode and shows the result.
“Percentage” questions come in a few different shapes, and this calculator covers the three most common: finding X% of a number, figuring out what percent one number is of another, and finding the percentage increase or decrease between two values.
Example
“What is 15% of 80?” → 15% × 80 = 12. “40 is what percent of 200?” → 40 ÷ 200 = 20%. “Percentage change from 50 to 65” → (65 − 50) ÷ 50 = 30% increase.
Limitations
This is a general-purpose math tool — for specific finance calculations like discounts or tax, the dedicated Discount and Sales Tax calculators show more relevant context alongside the math.
Frequently asked questions
How do I calculate X% of a number?
Multiply the number by the percentage divided by 100. For example, 15% of 80 = 80 × (15 ÷ 100) = 12.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 40 is what percent of 200? → (40 ÷ 200) × 100 = 20%.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, and multiply by 100. A positive result is an increase; a negative result is a decrease.
Why does percentage change use the original value as the base?
Percentage change is always relative to the starting point, so the original (not the new) value is the denominator — this is a common source of confusion, especially with decreases.