Empirical Formula Calculator
Calculate the empirical formula of a compound from percent composition or mass data. Enter the elements and their percentages or masses to find the simplest whole-number ratio.
Published by:
isCalculator Editorial Team
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How to use this tool?
This calculator determines the empirical formula (simplest whole-number ratio of atoms) from mass or percentage composition data.
- Set number of elements (2–5) using the input field at the top.
- Enter element symbols (e.g., C, H, O) in the Element fields. Use standard periodic table abbreviations.
- Enter mass values in the Mass / % fields. You can use either:
- Percentages (%) – must sum to ~100%.
- Grams (g) – actual masses from a sample.
- Select the unit (% or g) for each element from the dropdown.
- Click "Calculate Empirical Formula".
Output: The empirical formula (e.g., CH₂O) appears in green. Below it, a step-by-step breakdown shows mole calculations and ratio rounding.
Tip: If percentages don’t sum to 100% (within 0.5%), the calculator will warn you. For gram inputs, no total check is performed.
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Frequently Asked Questions
An empirical formula represents the simplest whole-number ratio of atoms of each element in a compound. For example, hydrogen peroxide (H2O2) has an empirical formula of HO.
Enter the number of elements (2-5), then input each element symbol (e.g., C, H, O) and its mass in grams or percentage. Click 'Calculate Empirical Formula' to get the result.
If you enter all percentages, they should sum to approximately 100%. The calculator will warn you if the sum is off by more than 0.5%. You can also enter masses in grams instead.