Percentage Calculator
Five percentage calculations in one tool: percent of a number, what percent one value is of another, percentage increase or decrease, and percentage difference.
No uploads • No tracking • No registration
How It Works
Pick a calculation mode
Choose the type of percentage question you're answering.
Enter your numbers
Type any values, including decimals and negatives where they apply.
Read the result and formula
The answer updates instantly, with the exact formula used shown underneath.
Privacy note: every calculation runs locally in your browser. Nothing you enter is sent to a server.
Examples
Frequently Asked Questions
How do I calculate what X% of Y is?+
Multiply Y by X and divide by 100. For example, 20% of 500 is (20 × 500) ÷ 100 = 100.
How do I find what percent one number is of another?+
Divide the first number by the second, then multiply by 100. For example, 50 is what percent of 200? (50 ÷ 200) × 100 = 25%.
What's the difference between percentage change and percentage difference?+
Percentage change is directional — it compares a "from" value to a "to" value and can be positive (increase) or negative (decrease). Percentage difference is symmetric — it compares two values against their average and is always expressed as a positive number, regardless of which value you list first.
Why is a 20% increase followed by a 20% decrease not back to the original number?+
Because each percentage is calculated on a different base. Increasing 100 by 20% gives 120, but decreasing 120 by 20% gives 96, not 100, since 20% of 120 is larger than 20% of 100.
Can this calculator handle negative numbers?+
Yes, for modes where negative values make sense — such as comparing a loss to a starting value in the increase/decrease mode. Fields that shouldn't be zero (like a percentage-of base) are validated to avoid division by zero.
How is percentage increase or decrease calculated?+
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is an increase; a negative result is a decrease.
Does this tool store the numbers I enter?+
No. Every calculation runs locally in your browser with plain JavaScript. Nothing is sent to a server or saved.