Molarity & Dilution Calculator — Free Science Calculator

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Molarity Calculation

M = n / V

Formulas

M = n / V

M = molarity (mol/L), n = amount of substance (mol), V = volume (L). n = mass (g) ÷ molar mass (g/mol).

M₁V₁ = M₂V₂

M₁V₁ = M₂V₂ — conservation of moles during dilution.

What Is Molarity?

Molarity vs. Molality

Molarity (M, mol/L) is moles of solute per liter of solution — the most common concentration unit in lab chemistry. Molality (m, mol/kg) uses mass of solvent instead and is temperature-independent. For dilute aqueous solutions, M ≈ m.

The Dilution Formula

M₁V₁ = M₂V₂ expresses conservation of moles: the amount of solute stays the same before and after adding solvent. It is the foundation of all serial dilutions, standard curve preparation, and stock solution work.

Mass → Moles Conversion

n = m / M. To find the number of moles from a weighed mass, divide by the molar mass (g/mol). Enter the chemical formula to auto-compute the molar mass from IUPAC 2021 atomic weights — or provide your own value.

Real-World Applications

Used daily in: preparing lab reagents (1 M HCl, 0.1 M NaOH), making buffer solutions, serial dilutions for calibration curves, pharmaceutical formulation, cell culture media, and titrations.

Frequently Asked Questions

Do I need to enter a chemical formula?
No — the formula field is optional. If you know the solute's molar mass, just enter the mass and volume directly. If you enter a formula (e.g. NaCl), the molar mass is computed automatically from IUPAC 2021 atomic weights.
What volume units are supported?
Liters (L), milliliters (mL), and microliters (μL). The calculator automatically converts between units. Enter your volume in any unit — results are always in standard SI units (mol/L, g/L).
How does the dilution calculator work?
Fill any 3 of the 4 fields (M₁, V₁, M₂, V₂). Leave the 4th field empty — it will be automatically computed using M₁V₁ = M₂V₂. The auto-computed field is highlighted in green. Clear a field to make it the new unknown.
Can I use this for serial dilutions?
Yes. For a 10-fold serial dilution: enter M₁ = your stock concentration, V₁ = 1 (to make 1 mL), M₂ = M₁/10. The calculator gives you the total volume V₂ needed. Add solvent to reach V₂.

Explore Related Tools

Molar Mass

Percent Composition

Atomic Weight

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Zero Upload — calculated entirely in your browser · We do not record your financial data or employee count. All calculations are performed instantly in your browser.