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What does this calculator estimate?
An empirical formula calculator finds the simplest whole-number ratio of elements in a compound. Enter each element and its mass (e.g., 'C:2.5, H:0.42, O:3.33') to get the empirical formula.
- Empirical formula = simplest whole-number ratio
- moles = mass ÷ atomic mass
- CH₂O is the empirical formula of glucose
What an empirical formula is
The empirical formula shows the simplest whole-number ratio of atoms, not the actual molecule size. Glucose (C₆H₁₂O₆), for example, has the empirical formula CH₂O. Converting masses to moles and reducing the ratio gives it.
Limitations to watch for
The tool needs masses in grams of each element — percentages can be used by treating them as grams per 100 g. Experimental data has error; ratios near whole numbers (1.98, 3.05) should be rounded. The empirical formula differs from the molecular formula.
How to use it in practice
Enter the measured masses (or % composition as grams per 100 g). The tool converts to moles and reduces. To find the molecular formula, divide the molecular weight by the empirical formula weight.
['Enter each element symbol and its mass.', 'Separate entries with commas (C:2.5, H:0.42, O:3.33).', 'The tool reduces to the simplest whole-number ratio.']
How this calculator works
Formula
Moles of each element = mass ÷ atomic mass. Divide every mole count by the smallest to get the ratio; multiply by the smallest integer to clear fractions. The result is the empirical formula (simplest whole-number ratio).
Worked example
2.50 g C, 0.42 g H, 3.33 g O: moles = 0.208 C, 0.417 H, 0.208 O → ratio 1:2:1 → CH₂O.
Assumptions to verify
- Masses are in grams (or % as per-100-g).
- The element list covers the whole compound.
- Atomic masses are the standard values.
Frequently asked questions
What is an empirical formula?
The simplest whole-number ratio of atoms in a compound. Water is H₂O; hydrogen peroxide is HO (empirical) but H₂O₂ (molecular).
How do I find it?
Convert each element's mass to moles (mass ÷ atomic mass), divide by the smallest, and round to whole numbers. C 0.208, H 0.417, O 0.208 → CH₂O.
What's the difference between empirical and molecular?
Empirical is the ratio; molecular is the actual atom count. Glucose is CH₂O (empirical) but C₆H₁₂O₆ (molecular).
Can I use percent composition?
Yes — treat percentages as grams per 100 g of compound.
What if the ratio is 1.5 or 2.33?
Multiply everything by the smallest integer to clear fractions: 1.5 → ×2 = 3, 2.33 → ×3 = 7.
What is CH₂O?
The empirical formula of glucose and many sugars — 1 carbon, 2 hydrogens, 1 oxygen per ratio unit.
How do I get the molecular formula?
Divide the molecular weight by the empirical formula weight, then multiply the empirical subscripts by that integer.
Cite this tool
BoringToolsKit. “Empirical Formula Calculator.” boringtoolskit.com/empirical-formula-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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