Molarity Calculator
Calculate molarity, moles, and solution concentrations for chemistry
Molarity
mol/L
Solution Steps
- Convert volume: 1 L = 1.000 L
- Apply formula: M = n / V
- M = 0.5 mol / 1.000 L
- M = 0.5000 mol/L
Quick Reference
Common Conversions
Key Relationships
How it works
Molarity expresses the concentration of a solution as moles of solute per litre of solution. The calculator finds any one of molarity, moles, or volume from the other two, which is the backbone of preparing chemical solutions.
Molarity
M = moles of solute ÷ litres of solution
- M
- molarity (mol/L)
- moles
- amount of solute
- litres
- total solution volume
Worked example
- 0.5 mol of solute
- Dissolved to make 2 L of solution
- M = 0.5 ÷ 2
0.25 M (mol/L).
Good to know
- Volume is the final solution volume, not just the solvent you added.
- To get moles from mass, divide grams by the molar mass.
- Diluting follows M₁V₁ = M₂V₂ — concentration down, volume up, moles unchanged.
Related Calculators
Frequently Asked Questions
What is molarity?
Molarity (M) is the concentration of a solution expressed as moles of solute per liter of solution: M = n ÷ V. A 1 M solution contains one mole of solute in each liter of solution.
How do I calculate molarity from grams?
Convert mass to moles using the molar mass, then divide by solution volume in liters. For 58.44 g of NaCl (molar mass 58.44 g/mol) dissolved to make 0.5 L: n = 1 mol, so M = 1 ÷ 0.5 = 2 M.
What's the difference between molarity and molality?
Molarity is moles per liter of solution; molality is moles per kilogram of solvent. Molality doesn't change with temperature because mass is constant, while molarity shifts slightly as the solution expands or contracts.
How do I dilute a solution to a target molarity?
Use M₁V₁ = M₂V₂. To make 250 mL of 0.1 M solution from a 1 M stock: V₁ = (0.1 × 250) ÷ 1 = 25 mL of stock, then add solvent up to 250 mL total. Always add acid to water, never the reverse.
How do I prepare a solution of a specific molarity from solid?
Calculate the mass needed: mass = molarity × volume (L) × molar mass. Dissolve that mass in less solvent than the final volume, then fill to the mark in a volumetric flask — dissolving can change volume, so never start with the full amount of solvent.