When to use this calculator
Convert a substance’s mass into amount of substance using its molar mass. Use the molar mass for the exact chemical formula and composition.
Explore the concentration & mixtures calculators for other questions in this topic. For a related calculation, use the Parts Per Million Calculator: Calculate mass-based ppm from solute and total mixture masses.
PUTTING IT INTO PRACTICE
Moles: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Mass (g) | 18 |
| Molar mass (g/mol) | 18.01528 |
| Result | 0.999152 mol |
- Check the input labels and enter the example values above.
- Apply the relationship: Moles = mass ÷ molar mass.
- The result is 0.999152 mol, rounded for display.
How to interpret your result
Use the molar mass for the exact chemical formula and composition.
Keep mass, amount and volume definitions separate. Molarity uses final solution volume; molality uses solvent mass. A dilution cannot increase concentration without some process beyond adding solvent.
Frequently asked questions
Are molarity and molality interchangeable?
No. Molarity is amount per solution volume, while molality is amount per solvent mass.
How do I use the moles calculator?
Enter mass (g), molar mass (g/mol). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Moles = mass ÷ molar mass.
What should I check before using the result?
Use the molar mass for the exact chemical formula and composition.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see OpenStax: molarity and dilution ↗. This is a topic reference, not an external review or endorsement of this tool.
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