Oxygen Partial Pressure (ppO2) Calculator
Check the oxygen partial pressure your gas delivers at a given depth. ppO2 drives oxygen toxicity risk, and recreational divers keep it at or below 1.4 ata while working.
How to calculate oxygen partial pressure
- Enter the oxygen percentage of your gas, for example 21 for air or 32 for EAN32.
- Enter the depth in metres or feet.
- Read the ppO2 in ata and check whether it stays within the 1.4 working limit.
Examples
EAN32 at 30 m
Oxygen 32%, depth 30 m
ata 4.0, ppO2 1.28 (within limit)
EAN32 at 40 m
Oxygen 32%, depth 40 m
ata 5.0, ppO2 1.6 (over limit)
Frequently asked questions
What is oxygen partial pressure in diving?
ppO2 is the share of the total breathing pressure made up by oxygen. At depth the total pressure rises, so ppO2 rises with it, and a high ppO2 is what drives oxygen toxicity risk.
How is ppO2 calculated?
Find ambient pressure first: ata is depth in metres over 10 plus 1, or depth in feet over 33 plus 1. Then ppO2 is oxygen percent over 100, times ata. Air at 30 m gives 0.21 times 4 = 0.84 ata.
What ppO2 is safe for recreational diving?
Recreational training keeps the working ppO2 at or below 1.4 ata, with 1.6 ata reserved for short contingency segments. This tool flags whether your ppO2 is within the 1.4 limit.
What happens if ppO2 gets too high?
A high ppO2 raises the risk of central nervous system oxygen toxicity, which can cause convulsions underwater and is often fatal. This is why mixes have a maximum operating depth.
Can I rely on this tool instead of training?
No. This is a training and planning aid only. Get certified, analyse every cylinder, follow your training and defer to your dive computer and tables in the water.
Related tools
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Find the maximum operating depth of any nitrox mix in metres and feet. Set the oxygen percentage and your ppO2 limit, default 1.4 ata. Free planning aid.
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Equivalent Air Depth Calculator
Convert a nitrox dive to its equivalent air depth in metres or feet. Enter the oxygen percentage and depth to read the EAD for table and computer planning.
Scuba Air Consumption Calculator
Work out your surface air consumption rate from a dive. Enter start and end pressure, time and depth to get a SAC rate in psi or bar per minute for planning.