The molarity calculator computes concentration (mol/L), moles, mass, or volume of solutions using M = n/V. Enter molecular weight and any three of the four variables. Ideal for solution preparation in chemistry labs.
Molarity Calculator (M = n/V)
How to Use the Molarity Calculator
This calculator solves for molarity, moles, mass, or volume given the other three values and the compound's molar mass.
Preparing a Solution
To prepare 250 mL of 0.5 M NaCl (molar mass 58.44 g/mol): mass = M × V × M_r = 0.5 × 0.25 × 58.44 = 7.305 g. Weigh 7.305 g NaCl and dissolve in enough water to reach 250 mL total volume.
Finding Molarity from Mass
10 g NaCl dissolved in 0.5 L: n = 10/58.44 = 0.171 mol. M = 0.171/0.5 = 0.342 mol/L.
Molar Mass Input
Use the Molecular Weight Calculator on this site to find the molar mass of your compound, then enter it in this tool.
FAQ
What is molarity?
Molarity (M) is the number of moles of solute per liter of solution: M = n/V. A 1 M NaCl solution contains 1 mole (58.44 g) of NaCl in 1 liter of solution. Molarity is the most common concentration unit in chemistry. Note: molarity uses liters of solution (not solvent).
How do I prepare a 0.5 M NaCl solution?
Moles needed = M × V = 0.5 mol/L × 1 L = 0.5 mol. Mass = 0.5 mol × 58.44 g/mol = 29.22 g. Weigh 29.22 g of NaCl, add to a 1-liter volumetric flask, dissolve in some water, then add water to the 1-liter mark. Stir to mix.
Is this calculator free?
Yes, completely free with no signup required. All calculations run in your browser.
Is my data private?
Yes. All calculations run locally. Nothing is transmitted.
What is the difference between molarity and molality?
Molarity (M) = moles of solute / liters of solution. Molality (m) = moles of solute / kilograms of solvent. Molarity changes with temperature (as solution volume changes), while molality does not. For dilute aqueous solutions, M ≈ m. Molality is used in colligative property calculations (boiling/freezing point).