LazyTools

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🧉 Molarity Calculator

Solve any part of a solution’s concentration — molarity, mass, molar mass or volume — from M = n/V, with the molar mass auto-filled from a formula.

Mass of solute

7.305 g

M = n/V, with n = mass ÷ molar mass. Volume in litres. 🔒 Computed in your browser.
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How the molarity calculator works

Molarity is moles of solute per litre of solution: M = n/V, where n = mass ÷ molar mass. Enter any three of {mass, molar mass, volume, molarity} and the tool solves for the fourth. Type a chemical formula and the molar mass is computed automatically from atomic weights.

The everyday bench calculation for making up a solution. Enter the formula (e.g. NaCl) and the tool fills in 58.44 g/mol for you, then solves for the mass you need.

Frequently asked questions

How do I calculate molarity?

Molarity (mol/L) = moles of solute ÷ litres of solution, and moles = mass ÷ molar mass. For 5.85 g NaCl (58.44 g/mol) in 1 L: 0.1 mol ÷ 1 L = 0.1 M.

How much solute do I need for a target molarity?

mass = molarity × volume (L) × molar mass. For 0.5 M NaCl in 250 mL: 0.5 × 0.25 × 58.44 = 7.31 g. Enter the target and the tool computes the mass.

Can it find the molar mass for me?

Yes — type the chemical formula and the molar mass is calculated from atomic weights and filled in automatically.

What units does it use?

Molarity in mol/L (M), mass in grams, molar mass in g/mol, and volume in litres (enter mL as 0.25 L, or use the mL field).

What is the difference between molarity and molality?

Molarity is moles per litre of solution; molality is moles per kilogram of solvent. This tool computes molarity (M).

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