Enter the gas concentration in ppm and select the total pressure setting to determine the equivalent partial pressure in atmospheres (atm).
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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).
P_{gas} = \frac{ppm \times P_{total}}{10^6}Variables:
- Pgas is the partial pressure of the gas in atmospheres
- ppm is the gas concentration in parts per million
- Ptotal is the total system pressure in atmospheres
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. Since ppm is dimensionless and atm is a pressure unit, the conversion depends on the total pressure of the gas mixture. 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, determine the total pressure of the gas mixture in atmospheres.
- 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 how a concentration of 100 ppm converts to partial pressure in atm under several total pressure conditions.
| 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.