Percentage by Mass of an Element Calculator
⚗ Moles & Stoichiometry. Use the Percentage by mass of an element formula to find percentage by mass, ar of the element, atoms in the formula, mr of the compound: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Percentage by mass | % |
| Ar of the element | no unit |
| Atoms in the formula | no unit |
| Mr of the compound | no unit |
Worked example
Find the percentage by mass when Ar of the element = 40, Atoms in the formula = 1, Mr of the compound = 100.
Using \% = (Ar × number of atoms)/Mr × 100: Percentage by mass = 40 %.
Frequently asked questions
What is the formula for Percentage by mass of an element?
\% = (Ar × number of atoms)/Mr × 100.
What do the letters stand for, and what units are used?
Percentage by mass in %, Ar of the element, Atoms in the formula, Mr of the compound.
How do you calculate percentage by mass?
Put the values into \% = (Ar × number of atoms)/Mr × 100. For example, with Ar of the element = 40, Atoms in the formula = 1, Mr of the compound = 100, percentage by mass = 40 %.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (percentage by mass, ar of the element, atoms in the formula, mr of the compound) and fill in the others: it rearranges the formula for you.
