Molarity Calculator
Convert
Molarity (M) is the concentration of a solution in moles of solute per litre of solution: M = n / V, where the number of moles n is the solute mass divided by its molar mass. This calculator works in three directions. Give it the mass, molar mass and volume to get the molarity; give it the target molarity, volume and molar mass to get the mass you need to weigh out; or give it the mass, molar mass and molarity to get the volume to dilute to. Mass accepts mg/g/kg, volume mL/L and concentration mM/M, and the result auto-scales to sensible units. The moles of solute are shown alongside every answer.
Result
100 mM
Moles: 0.1 mol
Formula: M = (mass / molar mass) / volume
M = (mass / molar mass) / volume. Moles n = mass / molar mass. Concentration is moles of solute per litre of solution.
How to use
- Pick what to solve for: molarity, mass, or volume.
- Enter the molar mass of the solute (g/mol) and the two known quantities with their units.
- Read the result and the number of moles involved.
Frequently asked questions
- What is molarity?
- Molarity is moles of solute per litre of solution (mol/L, written M). A 1 M solution contains one mole of solute in each litre.
- How do I calculate molarity?
- M = n / V, where n = mass / molar mass and V is volume in litres. For example 5.844 g of NaCl (molar mass 58.44 g/mol) in 1 L is 0.1 mol / 1 L = 0.1 M.
- How much solute do I weigh for a target molarity?
- mass = molarity × volume × molar mass. To make 2 L of 0.5 M NaCl you need 0.5 × 2 × 58.44 = 58.44 g.
- Where do I find the molar mass?
- Sum the atomic masses of every atom in the formula. NaCl is 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol; many periodic-table references list it directly.
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