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Best Mix Calculator
for Nitrox

Warning: This Best Mix calculator is for aiding in the calculation of decompression obligations when diving using Nitrox. It is not suitable for calculating narcotic effects and decompression requirements when using Trimix or Heliox.

Disclaimer: I take no responsibility for the accuracy of the calculations and data below. Always verify against other sources.

This calculator can be used to find the Enriched Air Nitrox "Best Mix" (FO2) for dives with the planned maximum partial pressure of oxygen (ppO2) at the planned maximum diving depth in metres when breathing Enriched Air Nitrox. Just enter values for "Maximum Partial Pressure Oxygen (ppO2)" and "Maximum Depth" and click on the "Submit" button.

Best Mix Calculator
* Indicates required field

e.g. 1.2 to 1.6 bar

e.g. 33 metres

Diving with a planned Maximum Partial Pressure Oxygen (ppO2) of 1.4 bar at a planned Maximum Depth of 33 metres (108 feet)
your Nitrox Best Mix rounding down is:

0.32 FO2

or 32% - EAN32

This calculator provides information about gas use in scuba diving. UNDER NO CIRCUMSTANCES is there any implication that any gas mixture is safe or even life supporting at any depth. If you have not recived training in technical scuba diving, Nitrox, Trimix or Heliox you should not attempt to use any of these results. Improper use of gasses in diving can result in injury or DEATH.


We can calculate the "Best Mix" for when we dive using breathing gas mixtures that contain Nitrogen (N2) and Oxygen (O2) in different proportions to those in air. Such mixtures are known as Enriched Air Nitrox (EAN), or more commonly, Nitrox.

The Nitrox "Best Mix" is the highest fraction of oxygen (FO2) permissible in the gas mixture, based on a desired maximum partial pressure of oxygen (ppO2) when diving to a planned maximum diving depth.


To calculate the "Best Mix" using Nitrox for a specific maximum ppO2 and maximum diving depth, the following formula is used:

Metric - metres

Best Mix (FO2) = ppO2 / ((Depth / 10) + 1)

In which FO2 is the fraction of oxygen in the best mix Nitrox gas, ppO2 is the maximum desired partial pressure of oxygen in bar, and Depth is the planned maximum diving depth in metres. For example, if the maxium desrired partial pressure of oxygen is 1.4 and the planned maximum depth is 33 metres,
the Best Mix (FO2) is (1.4 / ((33 /10) + 1)) = .32 FO2.

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Last modified: Friday, 18 February 2011


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