MATH · PERCENTAGE
Percentage Calculator
Calculate X% of Y, percentage change between two values, or percentage difference. Three modes in one calculator.
About This Calculator
Percentages appear everywhere — discounts, tax, growth rates, statistical comparisons. This calculator covers the three most common percentage questions in a single page: finding a percentage of a number, calculating how much something changed, and comparing two values symmetrically.
How It Works
Select a mode: X% of Y gives a direct portion; % Change measures increase or decrease from one value to another (directional); % Difference compares two values without a direction (symmetric). All results are rounded to 4 decimal places.
The Formula
X% of Y = (X/100) × Y % Change = ((new − old) / |old|) × 100 % Difference = |a − b| / ((a+b)/2) × 100
- X
- the percentage
- Y
- the base value
Frequently Asked Questions
- What is the difference between % change and % difference?
- % Change is directional: it measures how much one specific value changed from a starting point. % Difference is symmetric: it compares two values without implying one came before the other (useful when both are measured at the same time).
- Why does % change show a negative number?
- A negative result means the new value is less than the old value — a decrease. For example, a price drop from $100 to $80 gives −20%.
- What if the old value is zero?
- The % change formula divides by the old value, so old = 0 causes division by zero. The calculator returns an error instead of an undefined result.