EXAMPLE
25% of 200 is 50.
Enter both values to see results.
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How this calculator works
Percentages show up everywhere in daily life — sale prices, tips, taxes, interest rates, grades. This calculator handles three common percentage problems: finding a percentage of a number, finding out what percentage one number is of another, and finding how much something went up or down. Pick the one you need, type in your two numbers, and the answer shows up right away.
THE MATH BEHIND IT
Percent of a number: (Percent ÷ 100) × Number
What percent one is of another: (Part ÷ Whole) × 100
Percent change: ((New − Old) ÷ Old) × 100
A real example
25% of 200:
Result
(25 ÷ 100) × 200 =50
Common questions
"Percent of" finds a piece of a number, like 20% of $50. "Percent change" applies when something starts at one number and ends at another. If there is no before-and-after, use "percent of." If there is one, use "percent change."
A negative result means the value decreased. If a price drops from $100 to $80, that is a −20% change. The minus sign indicates direction, not an error.
Find 10% of the starting number, then add it on. 10% of $50,000 is $5,000, so a 10% raise brings it to $55,000. This is the same as multiplying the original number by 1.10.
Use "compare two numbers" mode with 42 as the part and 50 as the whole: (42 ÷ 50) × 100 = 84%. The same math applies to anything scored out of a total, such as free throws made out of attempts.
This usually happens with rounding — if each percentage is rounded to a whole number before adding them, small fractions get lost and the total can land at 99% or 101%. It is a rounding artifact, not a calculation error.