When to use this calculator
Calculate molality using solute amount and solvent mass. Molality uses solvent mass and is different from molarity.
Explore the concentration & mixtures calculators for other questions in this topic. For a related calculation, use the Molar Mass From Sample Calculator: Recover molar mass from a known sample mass and amount of substance.
PUTTING IT INTO PRACTICE
Molality: 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 |
|---|---|
| Solute amount (mol) | 0.5 |
| Solvent mass (kg) | 2 |
| Result | 0.25 mol/kg |
- Check the input labels and enter the example values above.
- Apply the relationship: Molality = moles of solute ÷ kilograms of solvent.
- The result is 0.25 mol/kg, rounded for display.
How to interpret your result
Molality uses solvent mass and is different from molarity.
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 molality calculator?
Enter solute amount (mol), solvent mass (kg). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Molality = moles of solute ÷ kilograms of solvent.
What should I check before using the result?
Molality uses solvent mass and is different from molarity.
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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