Solve
Choose what you want to calculate and enter both values.
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Quick guide
Understand the calculation
Solves three readings of the same relationship: deriving a part from a percentage, expressing a part on a base of 100, and measuring change between two values. It accepts decimals and scientific notation, with 4 or 10 significant figures.
When to use this tool
Use “X % of” to obtain a part of a total; “What %?” to compare a part and its total; and “Change” when the rise or fall relative to the starting value matters. It covers yields, compositions, relative error, discounts, and changes between measurements.
How it works
“X % of” multiplies the total by p/100. “What %?” divides the part by the total and multiplies by 100. “Change” divides final−initial by the absolute starting value, so the sign still reports whether the quantity rose or fell when the starting point is negative.
The total cannot be 0 in “What %?”, nor the starting value in “Change”: without a base the quotient does not exist. Incomplete, invalid, or out-of-range entries are rejected explicitly.
Examples
- 15 % of 200
200 × 15/100 = 30 - 25 out of a total of 200
25/200 = 0.125 → 12.5 % - From −50 to −25
25/50 = 0.5 → +50 %
Frequently asked questions
How do I calculate the percentage increase between two values?
Choose Change and enter the starting and final values. A positive result means an increase; a negative one, a drop.
Is a percentage change the same as a difference in percentage points?
No. Moving from 20 % to 25 % is 5 percentage points, but a 25 % relative change. This tool calculates the latter.
Why is the change from a negative value positive?
Because the base uses the absolute starting value. From −50 to −25 the quantity rises, and the positive sign preserves that reading.