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Chemistry

Molality Calculator

Calculate moles of solute per kilogram of solvent from measured masses.

Explicit units and model assumptionsLocal calculations with worked examples
Chemistry workspace
Chemistry workspace

Check the units, concentration basis and assumptions before interpreting the result.

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Your chemistry result

Your result

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Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter solute mass, solute molar mass, solvent mass.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Molality = (solute mass ÷ solute molar mass) ÷ (solvent mass ÷ 1,000).

A WORKED EXAMPLE

Using solute mass = 10 g, solute molar mass = 58.44 g/mol, solvent mass = 500 g, the result is 0.342231348 mol/kg. Change these example inputs to match your task; use the method above to check each step.

Understanding your result

Its definition is moles of solute per kilogram of solvent. Unlike volume-based concentration, this ratio does not change simply because a solution expands with temperature.

What to keep in mind

Enter solvent mass only, excluding solute. Educational calculation only; use validated procedures for laboratory work.

Reference: OpenStax Chemistry 2e — chemical quantities and models

Common questions

Why does molality use solvent mass?

Its definition is moles of solute per kilogram of solvent. Unlike volume-based concentration, this ratio does not change simply because a solution expands with temperature.

Are my inputs uploaded?

No. This calculation runs in your browser without an account or an external API.

Methodology maintained by ClarityKit. How these tools are built and checked.