Molarity Calculator
Mass ↔ molarity ↔ volume
Molarity
0.103M
ƒ Molarity (M) = moles of solute ÷ litres of solution
Molarity is the concentration of a solution expressed as moles of solute per litre of solution (mol/L, symbol M). To find it, divide the mass of solute by its molecular weight to get moles, then divide by the volume in litres. This calculator solves for molarity, mass or volume — pick the unknown with the tabs, enter the rest, and the answer updates instantly.
How molarity is calculated
Molarity = (mass ÷ molecular weight) ÷ volume in litres. For caffeine (MW 194.19) at 1 g in 50 mL: moles = 1 ÷ 194.19 = 0.00515 mol; molarity = 0.00515 ÷ 0.05 L = 0.103 M.
The calculator handles unit conversions for you — mass in mg/g/kg, volume in mL/L, and concentration in M/mM/µM/nM.
What you use molarity for
Molarity is the standard way to specify reagent and buffer concentrations in a lab. You need it for reaction stoichiometry, for diluting stock solutions (see the Dilution calculator) and for preparing solutions to a target concentration (see Solution Preparation).
Frequently asked questions
What is molarity?
Molarity is the concentration of a solution given as moles of solute per litre of solution (mol/L, symbol M). A 1 M solution contains one mole of solute in every litre.
How do I prepare a 1 M solution?
Weigh out one molecular weight (in grams) of the compound, dissolve it, and make the solution up to one litre. For example, 1 M NaCl (MW 58.44) needs 58.44 g made up to 1 L.
Do I need the molecular weight?
Yes — molarity is mole-based, so converting between mass and moles requires the molecular weight. Use the Molecular Weight Calculator if you don't have it.
What's the difference between molarity and molality?
Molarity is moles per litre of solution; molality is moles per kilogram of solvent. Molarity changes slightly with temperature (volume expands); molality does not.
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