The concentration converter instantly converts between the six most common solution concentration units: molarity (M), molality (m), mass percent (w/w%), mole fraction (χ), ppm, and ppb. Enter a concentration in any unit along with the solute's molecular weight and solution density, and see all six values simultaneously.
Input
All Concentration Units
Conversion Formulas
How to Use the Concentration Converter
The concentration converter handles all standard solution concentration units in one place. Enter a value in any unit and see all six equivalent concentrations instantly — essential for analytical chemistry, biochemistry, and industrial laboratory work.
Step 1: Enter Your Concentration
Type the concentration value and select the input unit from the dropdown. Available units: molarity (mol/L), molality (mol/kg solvent), mass percent (g solute per 100g solution), mole fraction, ppm (mg/kg = mg/L for dilute aqueous solutions), and ppb.
Step 2: Enter Solute and Solvent Properties
The solute molecular weight (g/mol) is required for all conversions between mole-based and mass-based units. The solution density (g/mL) is needed to convert between volume-based molarity and mass-based molality. For pure water solvent, MW = 18.015 g/mol and density ≈ 1.00 g/mL. For concentrated solutions, use the actual density.
Worked Example: 1 M NaCl Solution
For 1 M NaCl (MW = 58.44 g/mol, density ≈ 1.04 g/mL at this concentration):
- Molarity: 1 M (input)
- Mass%: (1 mol × 58.44 g/mol) / (1040 g solution) × 100 ≈ 5.62%
- Molality: 1 mol / (1040g − 58.44g) × 1000 ≈ 1.019 m
- Mole fraction: 1 mol / (1 mol + 981.56/18.015 mol) ≈ 0.01804
- ppm: 5.62% × 10⁴ = 56,200 ppm
Understanding the Units
Molarity is the most common lab unit — it's easy to prepare by weighing and diluting to a known volume. Molality is used for colligative properties (boiling/freezing point changes) because it doesn't change with temperature. Mass percent appears in industrial contexts and on chemical safety data sheets. Mole fraction is used in physical chemistry for vapor pressure calculations (Raoult's law). ppm and ppb are standard in environmental and trace analysis where concentrations are extremely small.
FAQ
What is the difference between molarity and molality?
Molarity (M) is moles of solute per liter of solution — it changes with temperature as solution volume expands. Molality (m) is moles of solute per kilogram of solvent — it's temperature-independent. For dilute aqueous solutions, M ≈ m, but they diverge at high concentrations.
Is this calculator free?
Yes, completely free with no signup or account required. All calculations run in your browser.
Is my data private?
Yes. All calculations run locally in your browser. No data is sent to any server.
Why do I need to enter solute molecular weight?
Molecular weight converts between mass and moles. Without it, conversions between molarity/molality (mole-based) and mass% (mass-based) are impossible. For example, NaCl has MW = 58.44 g/mol.
Why do I need solution density?
Density converts between volume-based (molarity, mass% by volume) and mass-based (molality) concentrations. Aqueous solutions at dilute concentrations have density ≈ 1.00 g/mL, but concentrated solutions differ significantly — for example, 6M HCl has density ≈ 1.10 g/mL.
What is ppm in chemistry?
In solution chemistry, ppm (parts per million) typically means mg/L for dilute aqueous solutions, or (mass solute / mass solution) × 10⁶ by mass. This converter uses the mass-based definition: ppm = (mass solute / mass solution) × 10⁶.
What concentration unit should I use?
Use molarity (M) for most lab work and stoichiometry. Use molality (m) for colligative properties (boiling point elevation, freezing point depression). Use mass% for industrial processes. Use ppm/ppb for trace analyses and environmental chemistry.