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Percentage Calculator
Four common percentage calculations in one place — find a percentage of a number, what percent one number is of another, percentage change, or add/subtract a percentage.
Understanding Percentages
% of a Number
Multiply the number by the percentage divided by 100 — e.g. 20% of 500 = 500 × 0.20 = 100.
What % is X of Y
Divide X by Y and multiply by 100 — useful for scores, discounts, or completion rates.
Percentage Change
The difference between two values as a percentage of the original — shows growth or decline over time.
Add / Subtract %
Useful for calculating price increases, discounts, tips, or markups on any base amount.
How to Use the Percentage Calculator
Find a Percentage of a Number
Enter the percentage in the first field and the base number in the second field. The calculator instantly shows the value of that percentage.
Calculate What Percent One Number Is of Another
Enter the first number and the total number to find what percentage the first number represents.
Calculate Percentage Change
Enter the original value and the new value to instantly see the percentage increase or decrease between them.
Add or Subtract a Percentage
Enter a number, choose Plus or Minus, then enter the percentage. The calculator immediately displays the updated result.
Frequently Asked
Questions
1. How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, to find 20% of 500: (20 × 500) ÷ 100 = 100.
2. What's the difference between percentage change and percentage points?
Percentage change measures relative change (e.g. going from 80 to 100 is a 25% increase). Percentage points measure the raw difference between two percentages (e.g. going from 40% to 50% is a 10 percentage point increase, which is actually a 25% relative increase).
3. Why is a 50% decrease not undone by a 50% increase?
Because percentages are relative to different base values. If 100 decreases by 50%, it becomes 50. If that 50 then increases by 50%, it only becomes 75 — not back to 100 — because the second percentage is calculated on the smaller base.
4. Is my data private?
Yes. All calculations run entirely in your browser using JavaScript. Nothing you enter is ever sent to any server.
