Molarity (M) is the number of moles of solute dissolved per liter of solution, expressed as mol/L. It is the most common unit of concentration in chemistry. A 1 M (1 molar) solution of NaCl contains 58.44 grams of NaCl per liter of solution.

How do you calculate molarity?

Molarity = moles of solute ÷ liters of solution. To find moles first, divide the solute mass in grams by its molar mass in g/mol. For example, dissolving 5.85 g of NaCl (molar mass 58.44 g/mol) in 1 L of water gives 0.10 mol ÷ 1 L = 0.10 M.

What is the difference between molarity and molality?

Molarity (M) is moles of solute per liter of solution and changes with temperature (since volume expands/contracts). Molality (m) is moles of solute per kilogram of solvent and is temperature-independent. For most lab work at room temperature, molarity is used. Molality is used for colligative property calculations like boiling point elevation.

How many grams are in a 1 M solution?

It depends on the compound. A 1 M solution contains exactly 1 mole per liter, and 1 mole equals the molar mass in grams. For NaCl, 1 M = 58.44 g/L. For glucose (C₆H₁₂O₆), 1 M = 180.16 g/L. For HCl, 1 M = 36.46 g/L. Use this calculator to find the exact mass for any compound.

What is a 0.1 M solution?

A 0.1 M (100 mM) solution contains 0.1 moles of solute per liter of solution. This is 1/10 the concentration of a 1 M solution. For NaCl, a 0.1 M solution contains 5.844 g per liter — similar to physiological saline at 0.9% (0.154 M). Buffer solutions are commonly prepared at 0.1 M.

How do I prepare a 1 M NaCl solution?

To prepare 1 liter of 1 M NaCl: weigh out 58.44 g of NaCl, dissolve it in approximately 800 mL of deionized water, then bring the total volume to exactly 1 L in a volumetric flask. For a 0.5 M solution, use 29.22 g. Always add solute to solvent (not the reverse) to control concentration accurately.

Molarity Calculator — Moles, Mass & Volume

Calculates molarity, moles, mass, and volume for any solution — supports solving for any variable.

How to Calculate Molarity

The molarity calculator on this page solves for molarity, moles of solute, mass, or solution volume. Molarity (M) is the number of moles of solute per liter of solution. The formula is:

M = n / V — where n = moles of solute and V = volume in liters.

To find moles from mass, use: n = mass (g) ÷ molar mass (g/mol). The molar mass of a compound equals the sum of atomic masses of all atoms in the formula. For NaCl: Na (22.99) + Cl (35.45) = 58.44 g/mol.

Step-by-Step Example

Find the molar mass of your compound (e.g. NaCl = 58.44 g/mol)
Weigh out your solute in grams (e.g. 5.844 g)
Enter the solution volume in liters or mL (e.g. 0.5 L)
Calculate: n = 5.844 / 58.44 = 0.10 mol; M = 0.10 / 0.5 = 0.20 M

Molarity Formula and Units

The SI unit of molarity is mol/L, also written as M (molar). Common lab concentrations:

1 M — standard stock solutions (NaOH, HCl, NaCl)
0.1 M — typical buffer concentrations, diluted reagents
1 mM (0.001 M) — enzyme substrates, drug concentrations
1 µM (0.000001 M) — hormones, trace analytes

For diluting a concentrated stock solution, use our dilution calculator — it uses the C₁V₁ = C₂V₂ equation to find the final concentration after dilution.

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Common Molar Masses

Quick reference for frequent lab compounds:

NaCl — 58.44 g/mol (table salt, saline)
H₂O — 18.02 g/mol (water)
HCl — 36.46 g/mol (hydrochloric acid)
NaOH — 40.00 g/mol (sodium hydroxide)
H₂SO₄ — 98.08 g/mol (sulfuric acid)
Glucose (C₆H₁₂O₆) — 180.16 g/mol
Ethanol (C₂H₅OH) — 46.07 g/mol
Tris base — 121.14 g/mol (common buffer)

Molarity vs. Molality vs. Normality

These three concentration units are often confused in chemistry:

Molarity (M) — mol solute per liter of solution. Depends on temperature. Most common in general chemistry.
Molality (m) — mol solute per kilogram of solvent. Temperature-independent. Used for colligative properties.
Normality (N) — equivalents of solute per liter. Used in acid-base and redox reactions. N = M × equivalents per mole.

How to Prepare Solutions — Lab Tips

Always use a volumetric flask — it is calibrated for a specific volume at a specific temperature
Add solute to about 80% of the final volume of solvent, mix until dissolved, then bring to the final mark
For concentrated acids (H₂SO₄, HCl), always add acid to water, never the reverse
Label solutions with compound name, concentration, date, and preparer
Check if your compound is a hydrate (e.g. CuSO₄·5H₂O) — use the hydrate's molar mass

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Solving for Volume and Mass

This calculator supports three modes beyond finding molarity:

Find mass — enter molarity, volume, and molar mass to find grams needed
Find volume — enter molarity and moles (or mass) to find the volume required

These rearrangements of M = n/V are useful for solution preparation, dilution planning, and stoichiometry problems. For DNA and RNA melting temperature, see our Tm calculator which handles oligonucleotide concentrations in the context of hybridization.

Sources & References

IUPAC Compendium of Chemical Terminology — Molarity — International Union of Pure and Applied Chemistry
Analytical Chemistry: Quantitative Chemical Analysis — Daniel Harris / W.H. Freeman

Molarity Calculator