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Percent Composition Calculator
Find each element’s mass percent in a compound.
What a compound is made of
Percent composition breaks a compound down into the share of its mass each element contributes. It is a staple of chemistry, used to check formulas and plan reactions.
For water, the roughly 2 grams of hydrogen and 16 of oxygen give about 11.2% hydrogen and 88.8% oxygen by mass. Enter each element with its mass to see the breakdown.
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Frequently Asked Questions
What is percent composition?
The percentage of a compound’s total mass contributed by each element.
How do I enter data?
One element per line as a label and its total mass in the compound, like O 16.
How is it calculated?
Each element’s mass is divided by the total mass of all elements, times one hundred.
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