Molarity Calculator

Mass of solute (g)

Non-negative. Example: 5

Molar mass (g/mol)

e.g., NaCl = 58.44, Glucose = 180.156

Solution volume

Positive. Example: 250 mL or 0.25 L

You may drop a simple file like: mode=grams, grams=5, molar_mass=58.44, volume=250, vol_unit=mL or JSON.

Molarity – Quick Cheat Sheet

Definition: Molarity M = moles of solute / liters of solution.
From grams: moles = grams / molar mass (g ÷ g·mol⁻¹).
Volume units: convert mL → L by dividing by 1000.
Scaling: 1 M = 1000 mM = 1,000,000 µM.
Significant figures: match the least certain input (lab practice).
Common molar masses: NaCl 58.44; KCl 74.551; Glucose 180.156; Sucrose 342.296 g/mol.
Safety: Always add solute to (most of) the solvent, then bring to volume in a volumetric flask.

Worked examples

NaCl: 5 g in 250 mL → moles = 5/58.44 = 0.0855 mol; volume = 0.250 L → M = 0.342 M.
Glucose: 10 g in 100 mL → moles = 10/180.156 ≈ 0.0555 mol; volume = 0.100 L → M = 0.555 M.