Percent Composition Calculator

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Formula mode parses the chemical formula and splits each element automatically. Manual mode lets you enter any two masses directly.
Enter a standard chemical formula. Parentheses and hydrate dots are supported. Element symbols are case-sensitive (e.g. Co for cobalt, CO for carbon + oxygen).
Enter a symbol to show that element's mass percent as the primary result. Leave blank to use the first element in the formula.
Controls how many decimal places are shown in the percent results.
Mass percent (highlighted element)Minor component
27.29%
Molar mass of compound44.009g/mol
Distinct elements2
27.29% %
Trace component<10Minor component10-33Substantial33-67Major/dominant67+

C makes up 27.29% of CO2 by mass.

  • The molar mass of CO2 is 44.009 g/mol.
  • C accounts for 27.29% of that molar mass.
  • The compound has 2 distinct elements; all their percentages add to 100%.
  • Percent composition is independent of sample size: one gram or one kilogram of the compound has the same elemental percentages.

Next stepUse the full element-by-element breakdown below to check that all percentages sum to 100%, or work backward from the percentages to find an empirical formula.

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