Convert gaseous mg/m³, µg/m³, or g/m³ to ppm using molar mass in g/mol and actual temperature and pressure, or reverse-solve mass concentration or molar mass.

Ideal gases and vapors only. Enter actual gas temperature and absolute pressure. This conversion does not establish a safe exposure level.

g/mol To PPM Formula

For the gas calculator above, ppmv = mass concentration (mg/m³) × R × T / (P × MW), where R = 8.31446261815324 L·kPa/(mol·K), T is absolute temperature in K, P is absolute pressure in kPa and MW is molar mass in g/mol. The separate solution reference below uses a different concentration basis.

ppm (mg / L) = C × MW × 1000

Variables:

  • ppm is parts per million (often approximated as mg/L in dilute aqueous solutions)
  • C is the molar concentration (mol/L)
  • MW is the molar mass (g/mol)

For dilute aqueous solutions, the reference formula and table below use molarity × molar mass × 1000 to obtain mg/L. Numerically this approximates mass ppm only when solution density is about 1 kg/L. This solution calculation is separate from the gas calculator above.

Molarity (mol/L) to PPM (mg/L) Conversion Table (Assuming NaCl, molar mass = 58.44 g/mol)
Molarity (mol/L) Molar Mass (g/mol) PPM (≈ mg/L)
1.711e-658.440.1
8.556e-658.440.5
1.711e-558.441
3.422e-558.442
8.556e-558.445
1.711e-458.4410
3.422e-458.4420
4.278e-458.4425
5.133e-458.4430
6.845e-458.4440
8.556e-458.4450
0.001026758.4460
0.001283458.4475
0.001711158.44100
0.002566758.44150
0.003422358.44200
0.004277958.44250
0.008555758.44500
0.012833658.44750
0.017111458.441000
Formula used: ppm (mg/L) = Molarity (mol/L) × Molar Mass (g/mol) × 1000. “ppm ≈ mg/L” is a common approximation for dilute aqueous solutions.

What is g/mol To PPM?

“g/mol” is a unit of molar mass (molecular weight), not a concentration. In many chemistry problems, ppm is used as a concentration unit (often treated as mg/L for dilute aqueous solutions). Using the molar mass (g/mol), you can convert between molarity (mol/L) and ppm (≈ mg/L) for solutions. Note: ppm conversions for gases (ppmv) or for non-aqueous mixtures require additional information (such as temperature, pressure, or density).

How to Calculate g/mol To PPM?

The following steps describe the gas calculator above; the molarity-to-mg/L table is a separate solution reference.

  1. First, select the gas quantity to solve: ppmv, mass concentration or molar mass.
  2. Next, enter the other two gas quantities with their stated units.
  3. Enter gas temperature in °C or K and absolute pressure in atm or kPa, then select Calculate.
  4. The result is gas ppmv, not solution ppm by mass (mg/kg). For solutions, convert mg/L to mg/kg by dividing by solution density in kg/L.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Gas example at 25 °C and 1 atm absolute: the following inputs produce approximately 48.930807 ppmv.

Gas mass concentration = 100 mg/m³

Molar mass (MW) = 50 g/mol