What is Molarity?
Molarity, also known as molar concentration, measures the number of moles of solute per litre of solution. It is one of the most common units in chemistry, represented by the symbol M and the unit mol/L.
Molarity Formula
M = n / V where n = moles of solute, V = volume of solution in litres
Moles (n) can be found from mass: n = mass (g) / molar mass (g/mol). So the full formula becomes:
Molarity (M) = mass (g) / (molar mass (g/mol) × volume (L))
How to Use This Calculator
- Select calculation type: Choose whether you want to find Molarity, Mass, or Volume.
- Pick a common solute (optional): Select from the dropdown to auto‑fill the molar mass. You can still edit it.
- Fill the known values: Enter mass, volume (toggle L/mL), and molarity depending on your selection.
- Click "Calculate": The result appears instantly.
Example Calculations
1. Find molarity: 5.85 g of NaCl (58.44 g/mol) dissolved in 0.500 L of water.
M = 5.85 / (58.44 × 0.500) = 0.200 M
2. Find mass needed: Prepare 250 mL of 0.1 M NaOH (40.00 g/mol).
Mass = 0.1 mol/L × 0.250 L × 40.00 g/mol = 1.00 g
Frequently Asked Questions
What is the difference between molarity and molality?
Molarity (M) uses litres of solution, while molality (m) uses kilograms of solvent. Molarity depends on temperature because volume changes; molality is temperature‑independent.
Can I use the calculator for dilution problems?
Yes, indirectly. Use the mass calculation to find the mass of solute needed for a desired concentration, then dilute accordingly. For dilution from a stock solution, the formula M₁V₁ = M₂V₂ is more appropriate.
What units of volume are accepted?
The calculator accepts litres (L) and millilitres (mL). It automatically converts mL to L for the calculation.
