Calculator
Molarity calculator
Molarity (M) is the concentration of solute in moles per litre of solution. Enter the mass, molecular weight, and volume — the calculator gives molarity in µM, mM or M.
Molarity
17.22 mM
How does this calculator work?
The formula is M = (mass ÷ MW) ÷ V. Mass is in grams, MW (molecular weight) is in grams per mole, and V is in litres. The result is moles of solute per litre of solution.
Worked example
For 1 g of NaCl (MW 58.44 g/mol) in 100 mL water: (1 ÷ 58.44) ÷ 0.1 = 0.171 M, or 171 mM.
Working backwards: how much to weigh
To make 50 mL of 0.25 M NaCl (MW 58.44 g/mol), rearrange to mass = M × V × MW: 0.25 × 0.050 × 58.44 = 0.731 g. Dissolve it and make up to 50 mL.
Common mistakes
- Using the volume of solvent added instead of the final volume of solution.
- Using the anhydrous molecular weight for a hydrate (e.g. CuSO₄·5H₂O is 249.69 g/mol, not 159.61).
- Leaving the volume in mL: divide by 1,000 to get litres.
Learn the concept
FAQ
What is molarity?
Molarity (M) is the concentration of a solute expressed as moles per litre of solution. M = (mass ÷ molecular weight) ÷ volume.
How do I calculate molarity?
Divide the mass of solute (in grams) by its molecular weight (g/mol), then divide that by the solution volume (in litres).
What units does this calculator accept?
Mass in grams, molecular weight in g/mol, volume in mL, L, or µL. The result is shown in µM, mM, or M depending on scale.
Where do I find a chemical's molecular weight?
On any Molekula product page (Identification tab), or on PubChem / CAS Common Chemistry.
Does Molekula sell at custom molarities?
Yes — many products can be prepared in custom solvents and molarities on request. Use the Get-a-quote button on any product page.