Molality Calculator

m = moles solute / kg solvent. Used in colligative-property calculations (boiling-point elevation, freezing-point depression).

Inputs

Result

Loading calculator…
—

How to use this calculator

  • Enter moles of solute and kilograms of solvent.
  • Read molality.

About this calculator

Molality is moles of solute per kilogram of solvent (note: solvent only, not solution). Unlike molarity, molality doesn't change with temperature because mass doesn't change with temperature. Used in colligative properties: ΔT_b = K_b × m, ΔT_f = K_f × m.

Frequently asked

Molality vs molarity?+
Molality uses solvent mass, molarity uses solution volume. Molality is constant with temperature; molarity isn't.
When use molality?+
Boiling-point elevation, freezing-point depression, osmotic-pressure calculations — anywhere temperature varies.
Are molality and molarity ever equal?+
For dilute aqueous solutions at 4°C they're very close (water density ≈ 1.00 g/mL). For concentrated or non-aqueous solutions they differ significantly.
How does adding solute affect kg?+
kg refers to solvent only — adding solute doesn't change the solvent mass. Total solution mass = solvent mass + solute mass.
Why "m" lowercase?+
Capital M is reserved for molarity. Lowercase m for molality. Don't confuse them.

Related calculators

Molarity Calculator
M = moles solute / liters solution. The most common solution-concentration unit in chemistry.
Molar Mass Calculator
Compute molar mass from a chemical formula. Supports common elements; multi-character symbols and subscripts.
Mole ↔ Gram Conversion
Convert between moles and grams using molar mass.
Dilution Calculator (M₁V₁ = M₂V₂)
Find target volume or concentration when diluting a stock solution.
pH Calculator (from [H⁺])
pH = -log[H⁺]. Compute pH from hydrogen-ion concentration in mol/L.
Ideal Gas Law (PV = nRT)
Solve for any of P, V, n, T given the other three. R = 8.314 J/(mol·K).

More tools you might like

Hand-picked tools that pair well with this one — same audience, same intent.

Molarity Calculator
Calc

M = moles solute / liters solution. The most common solution-concentration unit in chemistry.

Mole ↔ Gram Conversion
Calc

Convert between moles and grams using molar mass.

Molar Mass Calculator
Calc

Compute molar mass from a chemical formula. Supports common elements; multi-character symbols and subscripts.

Dilution Calculator (M₁V₁ = M₂V₂)
Calc

Find target volume or concentration when diluting a stock solution.

pH Calculator (from [H⁺])
Calc

pH = -log[H⁺]. Compute pH from hydrogen-ion concentration in mol/L.

Bates Numbering
PDF

Add Bates-style sequential numbering to a PDF — used in legal e-discovery and document production.