Convert gas ppm by mole and total absolute pressure to partial pressure in atm, with illustrative pressure presets or a custom value and Pa or mmHg equivalents.
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ppm to atm Formula
The following formula is used to convert a gas concentration in parts per million (ppm) into partial pressure in atmospheres (atm).
Variables:
- Pgas is the partial pressure of the gas in atmospheres
- ppm is the gas amount fraction in micromoles per mole (ppmv under the ideal-gas assumption), from 0 to 1,000,000; mass ppm is a different quantity
- Ptotal is the total absolute system pressure in atmospheres, not gauge pressure
To calculate the partial pressure in atm, multiply the ppm concentration by the total pressure in atm and divide by 1,000,000.
What is ppm to atm Conversion?
ppm to atm conversion is used to translate a gas concentration expressed as a mixing ratio into its corresponding partial pressure. For an ideal-gas mixture, ppm by mole is dimensionless and atm is a pressure unit, so the conversion depends on total absolute pressure. Mass ppm cannot be substituted directly; dissolved gases and real-gas corrections require other models. At standard atmospheric pressure, 1 ppm is equal to 1×10-6 atm. If the total pressure changes, the partial pressure changes in direct proportion.
How to Convert ppm to atm?
The following steps outline how to convert ppm to atm.
- First, determine the gas concentration in ppm.
- Next, select an illustrative pressure preset or enter the gas mixture’s measured total absolute pressure and its unit.
- Then use the formula Pgas = (ppm × Ptotal) / 106.
- After calculating the result, verify your answer with the converter above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
ppm = 100
Total Pressure = 1 atm
Partial Pressure = (100 × 1) / 1,000,000 = 0.0001 atm
ppm to atm Conversion Table
The table below shows 100 ppm by mole at illustrative total absolute pressures. Environment labels are approximate examples; actual pressure must be measured or otherwise established for the application.
| Environment | Total Pressure (atm) | 100 ppm in atm |
|---|---|---|
| Very high altitude | 0.5 | 0.00005 atm |
| Aircraft cabin | 0.75 | 0.000075 atm |
| Sea level (standard) | 1 | 0.0001 atm |
| Hyperbaric chamber | 2 | 0.0002 atm |
| Scuba dive at 30 m | 4 | 0.0004 atm |
Laboratory, environmental, engineering, and physiology work often reports gases in ppm, while pressure-based calculations require atm. Converting between these values makes it easier to compare concentrations across different pressure conditions and understand the true partial pressure of a gas in a mixture.
