Free Tool
Find the Optimal Nitrox or Trimix Blend for Any Depth
Enter your target depth and PPO2 limit — DiveKit instantly calculates the optimal nitrox or trimix blend, the maximum operating depth (MOD), and equivalent air depth (EAD). No guesswork, no tables, no internet required.
Free download — no account needed
What Best Mix Calculator Does
How DiveKit calculates the optimal gas mix for your target depth.
The Best Mix Calculator determines the ideal breathing gas composition for a given depth. For nitrox dives, it computes the maximum oxygen fraction (FO2) that keeps partial pressure within your PPO2 limit at the target depth — giving you the richest safe mix for maximum no-decompression time. For trimix dives, it also calculates the helium fraction needed to keep equivalent narcotic depth (END) within your comfort zone.
The calculator displays the maximum operating depth (MOD) for the computed mix so you can immediately verify the safety envelope. It supports both fresh water and salt water density, and lets you set custom PPO2 limits for bottom gas (typically 1.4 bar) and deco gas (up to 1.6 bar).
All calculations are based on Dalton's Law of Partial Pressures — the same physics your dive computer uses. Results update in real time as you adjust inputs, making it easy to compare options at the fill station or during dive briefings.
- Optimal nitrox blend for any target depth and PPO2 limit
- Trimix support — calculates both O2 and He fractions
- Shows MOD and EAD for the computed mix
- Fresh water and salt water modes
- Custom PPO2 limits for bottom and deco gas
- Real-time results as you adjust inputs
- Works 100% offline — no internet needed
Dalton's Law of Partial Pressures
The calculator applies Dalton's Law: the partial pressure of each gas in a mixture equals its fraction times the total ambient pressure. At depth, ambient pressure increases by roughly 1 bar per 10 meters of seawater. By setting a maximum PPO2 (typically 1.4 bar for bottom gas), the calculator solves for the highest safe oxygen fraction: FO2 = PPO2 / P_ambient. This gives you the richest possible nitrox mix — maximizing no-deco time while staying within oxygen toxicity limits.
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More free dive planning tools in DiveKit.
Try Best Mix Calculator Free
Download DiveKit free on iOS and Android. Best Mix Calculator is included — no account, no ads, no internet required.