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What does this calculator estimate?
A molar mass calculator computes the mass of one mole of a compound from its chemical formula. Enter a formula like H2O or CO2 to get the molar mass in g/mol.
- Molar mass = Σ (atomic mass × count)
- Units: g/mol
- H₂O = 18.02 g/mol; CO₂ = 44.01 g/mol
What molar mass is
The molar mass of a compound is the mass of one mole of it — the sum of its elements' atomic masses, each multiplied by its count in the formula. It's the conversion factor between grams and moles, the backbone of stoichiometry.
Limitations to watch for
The tool uses standard atomic weights (averages of isotopes). Formulas must be entered in a parseable form — hydrates, parentheses, and complex ions may need simplification. The result is for the pure substance; solvation doesn't change the formula mass.
How to use it in practice
Use molar mass to convert between mass and moles: grams ÷ molar mass = moles. It's needed for molarity, limiting-reagent, and yield calculations. Check the formula carefully — a wrong subscript changes the result.
['Enter the chemical formula (e.g., H2O, NaCl, CO2).', 'The tool sums the atomic masses of each element.', 'Use the result to convert grams to moles and back.']
How this calculator works
Formula
Molar mass = sum of (atomic mass × subscript count) for each element in the formula. Atomic masses are the standard periodic-table values in g/mol (H 1.008, C 12.011, O 15.999, etc.).
Worked example
Water H₂O: 2 × 1.008 (H) + 15.999 (O) = 18.02 g/mol. Carbon dioxide CO₂: 12.011 + 2 × 15.999 = 44.01 g/mol.
Assumptions to verify
- Standard atomic weights are used.
- The formula is entered without parentheses or hydrates.
- The compound is neutral and well-defined.
Frequently asked questions
What is molar mass?
The mass of one mole of a substance, expressed in g/mol. For water (H₂O) it's 18.02 g/mol.
How do I calculate molar mass?
Add each element's atomic mass multiplied by its count in the formula. CO₂ = 12.011 + 2×15.999 = 44.01 g/mol.
Why is it important?
It's the bridge between grams and moles — the unit chemists use to count particles. Grams ÷ molar mass = moles.
What is Avogadro's number?
6.022×10²³ — the number of particles in one mole. Molar mass is the mass of that many particles.
Does the tool handle hydrates?
No — enter the formula without water of hydration (e.g., CuSO4, not CuSO4·5H2O) and add the water separately if needed.
What are atomic masses?
The average mass of an element's naturally occurring isotopes in g/mol, from the periodic table (H 1.008, O 15.999, etc.).
Can I convert grams to moles with this?
Yes — divide the mass in grams by the molar mass to get moles, the standard stoichiometry step.
Cite this tool
BoringToolsKit. “Molar Mass Calculator.” boringtoolskit.com/molar-mass-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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