Molar Mass Calculator
Calculate a formula mass using standard approximate atomic masses for a supported set of elements in a simple chemical formula.
How to use this calculator
- Enter a simple formula such as H2O, CO2 or NaCl.
- Confirm that all inputs use the stated units and the same population, period or scope.
- Change one assumption at a time when comparing scenarios.
Formula used by the molar mass calculator calculator
Molar mass = sum of atomic masses × atom counts
- Molar mass = sum of atomic masses × atom counts
- This version does not parse parentheses, hydrates, isotope labels or every element; check formulas and atomic weights for precision work.
- Inputs are validated against required ranges and outputs are rounded for readability.
Worked examples
Worked example
H₂O contains two hydrogen atoms and one oxygen atom.
Water molar mass is about 18.015 g/mol.
Water molar mass is about 18.015 g/mol.
Understanding the result
Calculate a formula mass using standard approximate atomic masses for a supported set of elements in a simple chemical formula.
This version does not parse parentheses, hydrates, isotope labels or every element; check formulas and atomic weights for precision work.
Important notes
This version does not parse parentheses, hydrates, isotope labels or every element; check formulas and atomic weights for precision work.
Use the result as a calculation aid for the inputs supplied; confirm critical specifications independently.
Frequently asked questions
Are parentheses supported?
No; enter only a sequence of element symbols and integer counts in this version.
Why is my formula rejected?
It may contain an unsupported element, invalid symbol casing, grouping or notation.
How do I use this calculator?
Enter a simple formula such as H2O, CO2 or NaCl.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.