Gas Management

Nitrox Blending Calculator

Calculate ideal oxygen and air additions for an empty cylinder or a residual-gas top-up, with explicit impossible-fill results.

Blend inputs

Enter the analyzed residual gas and the desired fill. Pressure fields follow the independent pressure-unit preference.

Quick examples

Load a complete scenario, then adjust any value below.

Starting cylinder

Starting pressure

bar

Analyzed starting oxygen

At zero pressure, the starting analysis makes no contribution to the calculation.

Target fill

EAN32

Target pressure

bar

Target oxygen

Ideal partial-pressure blend

Pure oxygen addition

27.8 bar

Airaddition

172.2 bar

Predicted final mix

EAN32

Continuous-blending equivalent

Added gas: 32.00% O₂
O₂ feed /Airfeed: 1 : 6.18
Pure O₂ share of feed: 13.92%

This is the ideal feed ratio, not a compressor setting. Use only within the oxygen limit and procedure specified for the actual blending system.

Displayed fill pressures are rounded to 0.1 bar; the engine keeps unrounded values. Ideal mixing ignores temperature, real-gas behavior, gauge error, and bank-pressure limits.

A calculation is not a fill procedure

Pure oxygen creates a serious fire hazard. Blending requires suitable training and oxygen-clean, oxygen-compatible equipment and procedures. After the gas has mixed and cooled, analyze it with a calibrated oxygen analyzer, label the cylinder, and plan the dive from the measured mix.

Frequently Asked Questions

How much oxygen is needed for EAN32 at 200 bar?

Under the ideal partial-pressure model, an empty cylinder filled to 200 bar with EAN32 needs 27.85 bar of pure oxygen followed by 172.15 bar of air. Actual fills are affected by temperature, gauge accuracy, gas mixing, and real-gas behavior, so the cooled cylinder must be analyzed.

Can this calculator plan a Nitrox top-up over residual gas?

Yes. Enter the measured starting pressure and analyzed starting oxygen percentage. The calculation accounts for that residual oxygen before solving the oxygen and air additions.

Why can a Nitrox target be impossible?

With only pure oxygen and 21% air available, the gas being added must contain between 21% and 100% oxygen. Some residual-gas and target combinations require an added mix outside that range, or leave no pressure room for the required oxygen.

Is the calculated blend ready to dive?

No. It is an ideal-gas calculation, not a fill procedure or authorization to handle oxygen. A trained blender must use suitable oxygen-clean and oxygen-compatible equipment, then mix, cool, analyze, and label the cylinder. Plan from the measured mix.

Related Guides

Nitrox & oxygen

Nitrox Blending: Oxygen, Air, and Residual Gas

Learn how partial-pressure and continuous Nitrox blending account for residual gas, and why every calculated fill must still be analyzed.

Nitrox & oxygen

Best Nitrox Mix for Any Depth

Calculate the richest theoretical Nitrox mix for a planned depth and PPO2 limit, then learn how to apply the result safely.

Nitrox & oxygen

What is Nitrox? A Complete Guide for Divers

Learn what Nitrox is, how enriched air works, its benefits and risks, and why divers choose it.

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