PPM to Molarity Calculator — ppm to mol/L Converter
Convert a ppm mass concentration to molar concentration (mol/L) for any solute. Enter the ppm value, the molar mass of your compound, and the solution density — and get molarity, millimolar, micromolar, and nanomolar equivalents instantly.
ppm
g/mol
g/mL
Moles of solute per litre of solution: M = ppm × ρ / (1000 × Mw)
- 1
mg/L = ppm × density
100 × 1 = 100Multiply the mass-based ppm (mg/kg) by solution density (kg/L) to get mg per litre. - 2
g/L = mg/L ÷ 1000
100 ÷ 1000 = 0.1 - 3
Molarity = g/L ÷ molar mass
0.1 ÷ 58.44 = 0.001711
How does this calculator work?
Molarity = ppm × density / (1000 × molar mass). For 100 ppm NaCl (Mw = 58.44) in water: M = 100 / (1000 × 58.44) ≈ 1.71 mM. For non-water solvents, enter the actual solution density. Also shows mM, μM, and nM.
Formula
How this is calculated
The conversion from ppm to molarity links two different ways of expressing concentration. Parts per million (ppm, mass-based) says "how many mg of solute per kg of solution", while molarity (M) says "how many moles of solute per litre of solution".
The two-step conversion is: (1) multiply ppm by the solution density (g/mL ≈ kg/L) to get mg/L, then (2) divide by the molar mass of the solute in g/mol and by 1000 to convert mg to g. The result is M = ppm × ρ / (1000 × Mw). For dilute aqueous solutions (ρ ≈ 1.000 g/mL), the formula simplifies to M ≈ ppm / (1000 × Mw).
Typical examples: 100 ppm NaCl (Mw = 58.44 g/mol) in water gives 100 / (1000 × 58.44) ≈ 1.71 × 10⁻³ mol/L = 1.71 mM. The density correction matters for concentrated solutions or non-aqueous solvents — seawater at 1.025 g/mL gives results about 2.5 % higher than the dilute-water approximation.
Frequently asked questions
Add up the atomic masses of all atoms in the chemical formula (from the periodic table). Common examples: water H₂O = 18.02, sodium chloride NaCl = 58.44, glucose C₆H₁₂O₆ = 180.16, calcium carbonate CaCO₃ = 100.09. Many chemistry databases also list it directly.
For most environmental and water-quality samples, no — the density of tap or surface water is so close to 1.000 g/mL that the difference is smaller than measurement error. For highly saline water (seawater ≈ 1.025 g/mL), concentrated solutions, or organic solvents, use the actual density.
Rearrange the formula: ppm = M × Mw × 1000 / ρ. For example, 1 mM (0.001 mol/L) NaCl in water = 0.001 × 58.44 × 1000 / 1.000 = 58.44 mg/kg ≈ 58.44 ppm.
Also known as
TG we-Calculate Editorial Team. (2026). PPM to Molarity Calculator — ppm to mol/L Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/ppm-to-molarity-calculator
TG we-Calculate Editorial Team. "PPM to Molarity Calculator — ppm to mol/L Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/ppm-to-molarity-calculator.
TG we-Calculate Editorial Team, "PPM to Molarity Calculator — ppm to mol/L Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/ppm-to-molarity-calculator
@misc{wecalculate_ppm_to_molarity_calculator, title = {PPM to Molarity Calculator — ppm to mol/L Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/ppm-to-molarity-calculator}}, year = {2026}, note = {TG we-Calculate} }
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