What is X% of Y?
Multiply the Number by the Percentage and divide by 100. For example, 15% of 200 is 30.
Everyday percentage math
Percentage Calculator
Calculate percentages, increases or decreases, percentage change, and percentage difference with the formula shown for every valid result.
Private by design. Entered values and results stay in this browser page. The calculator does not upload your numbers or maintain a calculation history.
What is X% of a number?
One value is what percent of another?
Increase or decrease a starting value by a percentage.
How much did a value change from the original?
How different are two peer values?
What percent is one number of another?
Divide the Part by the Whole, then multiply by 100. A zero Whole is undefined because division by zero has no finite percentage result.
Increase or decrease by a percentage
For 250 increased by 12%, the change amount is 30 and the result is 280. A decrease above 100% can legitimately produce a negative mathematical result.
Percentage change uses the original value
Percentage change is directional: (New − Original) ÷ Original × 100. From 80 to 100 is a 25% increase.
Percentage difference is symmetric
When neither value is the baseline, this app divides the absolute difference by the average of the two values. 50 and 75 have a 40% percentage difference.
Percentage points are different
Moving from 40% to 50% is an increase of 10 percentage points, while the relative percentage change is 25%. This app does not add a separate percentage-points mode.
Exact and approximate results
Terminating decimal results are shown exactly through 12 decimal places. Other results use up to 6 decimal places, or scientific notation with up to 6 significant digits for tiny or very long values. Rounded answers are marked with ≈. Tiny non-zero values are never silently turned into zero.
Choose the right percentage tool
This general calculator does not replace dedicated Percent Off, Percent Error, Margin, Markup, body/weight, tax, finance, or academic percentage tools.
Change vs difference
Read Percentage Change vs Percentage Difference when the correct denominator is the part you are unsure about.
Use Original, not New, as the baseline
For a change from 80 to 100, divide the change of 20 by Original, 80: the increase is 25%. Dividing by New, 100, would answer a different question. Percentage difference instead uses the average and has no increase or decrease direction.
Equal percentage changes do not cancel
Increasing 100 by 50% gives 150. Decreasing 150 by 50% then gives 75, not 100, because the second percentage uses a different starting value.
Undefined does not mean zero
A zero Whole, a zero Original, or two zero values in percentage difference do not produce a finite answer. Treating these cases as 0% or Infinity would hide the missing denominator. A valid zero change between equal positive values is different.