Calculate empirical formula

Infer the simplest whole-number chemical formula from elemental mass percentages.

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ToolEmpirical Formula Calculator
Input
Output
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How it works

Each percentage is divided by atomic weight to obtain relative moles, values are divided by the smallest, and near-integer ratios become subscripts. An optional molar mass scales the empirical formula.

  • Percentages should total about 100%.
  • Atomic weights come from the stored element table.

Worked example

Water from its composition
11.19% hydrogen and 88.81% oxygen by mass
Input
											H 11.19,O 88.81
Output
												Empirical formula: H2O
Empirical mass: 18.02
Molecular formula: H2O
Molecular mass: 18.02
Multiplier: 1

When to use this

Combustion analysis infers simplest formula, lab reports convert mass percentages, and molecular-mass exercises scale empirical formulas.

Edge cases

  • Percentages far from 100% are rejected rather than silently renormalized.
  • Ratios such as 1:1.5 need an integer multiplier before rounding.
  • A non-integer molecular-mass multiple is not evidence for a valid molecular formula.