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Gas Blending

The Gas Blending calculator computes the exact fill sequence needed to mix a target gas from your current tank contents. It supports both nitrox and trimix blending using the partial pressure method.

Safety Notice

Gas blending requires specialized training and oxygen-clean equipment. Only blend gases if you are properly certified and equipped.

Freemium Tool

The Gas Blending calculator is free to try with a limited number of calculations. Premium subscribers get unlimited access.

Nitrox blending​

Nitrox blending uses the partial pressure method to calculate how much pure oxygen to add before topping off with air.

Inputs:

  • Current tank pressure and current O2 percentage: what is already in the tank
  • Target pressure and target O2 percentage: what you want to end up with

Output, step-by-step procedure:

  1. Add a specific amount of pure O2 (in bar or psi)
  2. Intermediate pressure after the O2 fill
  3. Top off with air to the target pressure
  4. Final mix composition

Trimix blending​

Trimix blending extends the process to three components: oxygen, helium, and nitrogen (which is supplied through the air top-off). The nitrogen fraction is calculated automatically as 100% minus O2% minus He%.

Inputs:

  • Current tank pressure, current O2 percentage, and current He percentage
  • Target pressure, target O2 percentage, and target He percentage

Output, step-by-step procedure:

  1. Add a specific amount of pure O2 (in bar or psi)
  2. Add a specific amount of pure He (in bar or psi)
  3. Top off with air to the target pressure
  4. Final mix composition

Bleed step for down-mixes and overpressure​

If the starting mix is too rich to reach the target by top-up alone — for example a down-mix like NX32 → NX28, or a starting pressure already above the target — the calculator inserts a bleed step as the first instruction. It tells you exactly how much pressure to vent from the tank before adding pure O2 (and helium for trimix) and topping off with air.

This ensures a valid fill sequence in every scenario, not just up-mixes.

Reading the results​

The results section breaks down each blending step with the exact pressures to add. This gives you a clear, actionable procedure to follow at the fill station.