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Molar mass calculator

Add each element count times its CIAAW abridged atomic weight to calculate molar mass and the mass of an entered amount.

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Answer

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Add each element count times its CIAAW abridged atomic weight to calculate molar mass and the mass of an entered amount.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Saved scenario
Save the current answer, then change an input to compare. This clears when you leave.
Formula and assumptions
Case-sensitive element symbols, parentheses, square brackets and hydrate dots are supported. No isotope labels, charges, fractional stoichiometry or enriched materials. Elements without a standard atomic weight fail explicitly. The uncertainty is the sum of count times tabulated uncertainty, not a statistical confidence interval. Values describe normal terrestrial materials.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
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Using Molar mass calculator
Add each element count times its CIAAW abridged atomic weight to calculate molar mass and the mass of an entered amount.
Case-sensitive element symbols, parentheses, square brackets and hydrate dots are supported. No isotope labels, charges, fractional stoichiometry or enriched materials. Elements without a standard atomic weight fail explicitly. The uncertainty is the sum of count times tabulated uncertainty, not a statistical confidence interval. Values describe normal terrestrial materials.
Next: Periodic table
Next: Molarity calculator
A worked example
For chemical formula = H2O, amount (mol) = 1, molar mass (g/mol) = 18.015.
Before you use the result
Case-sensitive element symbols, parentheses, square brackets and hydrate dots are supported. No isotope labels, charges, fractional stoichiometry or enriched materials. Elements without a standard atomic weight fail explicitly. The uncertainty is the sum of count times tabulated uncertainty, not a statistical confidence interval. Values describe normal terrestrial materials.
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ToolOctopus. “Molar mass calculator.” Updated 2026-09-29. https://tooloctopus.com/molar-mass-calculator.
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