Everyday math
Calculate percentages and percentage changes.
Choose a percentage question, enter the values, and see the answer with the formula used.
Your result
Enter two values to calculate.
Math used
The key idea
Percent means “per hundred.” Converting a percentage to a decimal divides it by 100, so 25% becomes 0.25. Finding 25% of 80 is therefore the same as multiplying 0.25 by 80.
Percent of a whole
Divide the part by the whole, then multiply by 100. If 20 of 80 items are selected, 20 / 80 x 100 = 25%.
Percentage change
Subtract the starting value from the ending value, divide by the absolute starting value, then multiply by 100. The starting value is the comparison base.
Percentage points differ
A rate moving from 20% to 25% rises 5 percentage points, but the relative increase is 25% because 5 is one quarter of the original 20.
Worked examples and comparison bases
For “what is 25% of 80,” the answer is 20. For “20 is what percent of 80,” the answer is 25%. For a change from 80 to 100, the increase is 25% because the original 80 is the comparison base.
When comparing rates, separate percentage points from percent change. A move from 20% to 25% is a 5-percentage-point increase and a 25% relative increase.
Assumptions and limits: this calculator performs general arithmetic. Rounding, measurement precision, negative values, and the meaning of the comparison base can affect how a percentage should be interpreted.
Method reviewed September 29, 2026.
Learn mode
Percent means part of a hundred
Try this question: What is 20% of $50?
Think first: Twenty percent means 20 out of every 100, so the answer should be one fifth of $50.
The method: $50 × 20 ÷ 100 = $10.
Remember: Always ask what the percentage is a percentage of; the comparison base changes the answer.
Keep calculating
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