Percentage Calculator
Percent of a number, percentage change, and X is what % of Y.
Formula
About this calculator
Percentages turn up everywhere — tips, discounts, tax, grades, interest, statistics — but the three core questions people ask are almost always the same. This calculator handles all three in one place so you never have to remember which number to divide by.
The first mode finds a percentage of a number (what is 15% of 80?). The second finds what percent one number is of another (12 is what percent of 48?). The third finds the percentage increase or decrease between two values, which is the one people get wrong most often because the change is always measured against the original value, not the new one.
Example: a price rising from $40 to $50 is a 25% increase, because the $10 change is measured against the original $40. But falling back from $50 to $40 is only a 20% decrease, because now the $10 is measured against $50. Same two numbers, different percentages — which is exactly why a reliable calculator beats mental math.
Frequently asked questions
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. Increases are positive; decreases are negative.
Why isn't a 25% rise cancelled by a 25% fall?
Because each percentage is measured against a different base. A rise is measured against the smaller original number, while the fall is measured against the larger new number.
How do I find what percent X is of Y?
Divide X by Y and multiply by 100. For example, 12 of 48 is 12 ÷ 48 × 100 = 25%.