Best Mix Calculator
for Nitrox

Warning: This Best Mix calculator is for aiding in the calculation of decompression obligations when scuba 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 scuba 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", then click on the "Submit" button.

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

Disclaimer:
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 use, you should not attempt to use any of these results. Improper use of gasses in scuba diving can result in serious injury or DEATH.

Best Mix Explanation

We can calculate the "Best Mix" for when we scuba 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.

Best Mix Formula

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.