Molarity Calculator

Calculate molarity (M) from moles of solute and liters of solution.

How It Works

Enter the moles of solute and the volume of solution in liters (or milliliters). The calculator divides moles by volume (converted to liters) to give molarity in mol/L. Select milliliters if that is your measured volume — the tool converts automatically.

Formula

Molarity (M) = moles of solute / liters of solution

Step-by-Step Example: Preparing a 2 M NaCl Solution

  1. Decide on a final volume, e.g., 500 mL (0.5 L)
  2. Calculate moles needed: 2 M × 0.5 L = 1 mol NaCl
  3. Convert to grams: 1 mol × 58.443 g/mol = 58.44 g
  4. Dissolve 58.44 g of NaCl in water and bring the total volume to 500 mL

Common Molarity Reference Values

Concentrated HCl ≈ 12 M | Concentrated H₂SO₄ ≈ 18 M | Seawater NaCl ≈ 0.6 M | Physiological saline ≈ 0.154 M | 1 M NaOH (standard titration) | 0.1 M HCl (dilute acid)

Molarity vs. Other Concentration Units

Molarity is the most widely used concentration unit in chemistry because it relates directly to mole ratios in reactions. However, it changes with temperature because liquid volume expands when heated. For temperature-sensitive work, molality (mol/kg solvent) or mass fraction (g/g) may be more appropriate. Normality (equivalents/L) is used in acid-base titrations and redox chemistry, where the equivalent depends on how many protons or electrons are transferred.

Preparing Serial Dilutions

To dilute a stock solution, use C₁V₁ = C₂V₂, where C is concentration and V is volume. For example, to make 100 mL of 0.1 M HCl from a 1 M stock: V₁ = (0.1 M × 100 mL) / 1 M = 10 mL. Take 10 mL of stock and add water to reach 100 mL total. Use our Dilution Calculator to automate this.

Frequently Asked Questions

What is molarity?

Molarity (M) is the concentration of a solution expressed as moles of solute per liter of solution. It is the most common unit of concentration in chemistry labs worldwide.

How do I calculate molarity from grams?

First convert grams to moles by dividing by molar mass, then divide by the volume in liters. Example: 58.44 g NaCl in 1 L: 58.44 ÷ 58.443 = 1 mol; 1 mol ÷ 1 L = 1 M.

What is the difference between molarity and molality?

Molarity (M) uses volume of solution (mol/L). Molality (m) uses mass of solvent (mol/kg). Molality does not change with temperature because mass is temperature-independent, while molarity does because volume changes with temperature.

What does a 1 molar solution mean?

A 1 M (one molar) solution contains 1 mole of solute dissolved in enough solvent to make exactly 1 liter of solution. For NaCl, that means 58.44 g dissolved and diluted to 1 L.

Can I enter milliliters instead of liters?

Yes. Select "Milliliters (mL)" from the volume unit dropdown, and the calculator will convert your volume to liters before computing molarity.