Enter the ppm concentration and select the gas or vapor into the calculator to determine the equivalent concentration in milligrams per cubic meter (mg/m³) at 25°C and 1 atm.
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ppm to mg/m³ Formula
The following formula is used to convert a gas concentration from parts per million (ppm) to milligrams per cubic meter (mg/m³) at 25°C and 1 atm.
mg/m^3 = ppm * MW / 24.45
For the reverse conversion, use ppm = mg/m³ × 24.45 ÷ MW.
Variables:
- mg/m³ is the concentration in milligrams per cubic meter
- ppm is the concentration in parts per million by volume
- MW is the molecular weight of the gas in g/mol
- 24.45 is the molar volume of an ideal gas at 25°C and 1 atm
To calculate mg/m³ from ppm, multiply the ppm value by the molecular weight of the gas and divide by 24.45.
What is ppm to mg/m³ Conversion?
ppm to mg/m³ conversion is used to translate a gas concentration from a volumetric basis to a mass-per-volume basis. Ppm represents the number of gas molecules present relative to air, while mg/m³ expresses the actual mass of the contaminant in each cubic meter of air. Because different gases have different molecular weights, the conversion depends on the specific substance being measured.
This type of conversion is common in occupational hygiene, indoor air quality, environmental monitoring, and regulatory compliance. Exposure limits and air quality standards may be reported in either ppm or mg/m³, so converting between the two helps compare results correctly.
How to Convert ppm to mg/m³?
The following steps outline how to convert ppm to mg/m³.
- First, determine the gas concentration in ppm.
- Next, determine the molecular weight (MW) of the gas in g/mol.
- Then, apply the formula mg/m³ = ppm × MW ÷ 24.45.
- Finally, compare the result to the value shown by the calculator above.
Common Molecular Weights
- CO: 28.01 g/mol
- CO₂: 44.01 g/mol
- SO₂: 64.07 g/mol
- NO₂: 46.01 g/mol
- O₃: 48.00 g/mol
- NH₃: 17.03 g/mol
- Benzene: 78.11 g/mol
ppm to mg/m³ Conversion Table
The following table shows example conversions for a 10 ppm concentration of several common gases at 25°C and 1 atm.
| Gas | Molecular Weight (g/mol) | 10 ppm in mg/m³ |
|---|---|---|
| Carbon Monoxide (CO) | 28.01 | 11.46 mg/m³ |
| Carbon Dioxide (CO₂) | 44.01 | 18.00 mg/m³ |
| Sulfur Dioxide (SO₂) | 64.07 | 26.20 mg/m³ |
| Nitrogen Dioxide (NO₂) | 46.01 | 18.82 mg/m³ |
| Ozone (O₃) | 48.00 | 19.63 mg/m³ |
| Ammonia (NH₃) | 17.03 | 6.97 mg/m³ |
| Benzene (C₆H₆) | 78.11 | 31.95 mg/m³ |
Heavier gases produce higher mg/m³ values for the same ppm concentration, while lighter gases produce lower mg/m³ values. That is why selecting the correct gas is essential for an accurate conversion.
Example Problem:
Use the following variables as an example problem to test your knowledge.
ppm = 10
Gas = Carbon Monoxide (CO)
MW = 28.01 g/mol
mg/m³ = 10 × 28.01 ÷ 24.45 = 11.46 mg/m³