Empirical Formula Calculator
Enter the percent by mass or the grams of each element to find a compound's empirical formula. The tool converts to moles, divides by the smallest, and reduces to whole numbers.
How to find an empirical formula
- Enter each element with its percent by mass, or its mass in grams.
- Each amount is divided by the atomic mass to get moles.
- Moles are divided by the smallest and scaled to the lowest whole number ratio.
Examples
Glucose empirical
40% C, 6.7% H, 53.3% O
CH2O
Two parts iron
69.9% Fe, 30.1% O
Fe2O3
Frequently asked questions
What is an empirical formula?
An empirical formula is the simplest whole number ratio of atoms in a compound. For example glucose, C6H12O6, has the empirical formula CH2O.
How is it calculated from percent composition?
Treat the percentages as grams in a 100 gram sample, divide each by its atomic mass to get moles, divide every value by the smallest, then scale to whole numbers.
What if a ratio comes out near 1.5 or 1.33?
The tool multiplies every ratio by the smallest integer that makes them whole, so 1.5 becomes a factor of two and 1.33 a factor of three, giving formulas like Fe2O3.
Can I enter grams instead of percentages?
Yes. Switch each element to mass and enter grams. The math is the same, since moles are mass divided by atomic mass either way.
Is the empirical formula the same as the molecular formula?
Not always. The molecular formula is a whole number multiple of the empirical formula. To find it you also need the compound molar mass.
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