Free Tool
Pick Nitrox or Trimix mode, set your target depth and PPO₂ limit, Dive Kit instantly returns the richest safe blend, MOD, equivalent air depth, equivalent narcotic depth, and gas density. Color-coded warnings flag oxygen toxicity, narcosis, and hard-to-breathe density before you commit to the mix.
Free download, no account needed
Optimal nitrox or trimix in two taps, with live safety stats at MOD.
The Best Mix Calculator picks the ideal breathing gas for a given depth, and tells you why. Switch between Nitrox and Trimix modes from a tab at the top. For nitrox, it computes the highest oxygen fraction (FO₂) that keeps partial pressure within your PPO₂ limit at the target depth, the richest safe mix, for maximum no-decompression time. For trimix, it adds helium to keep equivalent narcotic depth (END) within your comfort zone, and an optional max gas density constraint to keep work-of-breathing reasonable on deep dives.
Results are live. As you nudge depth, O₂%, He%, or END, the others recompute in real time, every input is bidirectionally coupled. The result panel shows the recommended mix in plain language ("Best Trimix: TMX 28/9" or "Best Nitrox: EAN35") plus full gas properties at MOD: PPO₂, equivalent air depth, equivalent narcotic depth, gas density (color-coded easy / elevated / hard to breathe), and EADD (density-equivalent depth).
Pick from PPO₂ presets (1.2 / 1.4 / 1.6) or set a custom value. Quick Fill loads any of your saved gas presets. Toggle whether O₂ is narcotic in the Diving settings for accurate END modeling. Trimix mode also surfaces the nearest standard mix (e.g. "Nearest standard: TMX 25/25") and the recommended depth range so you don't have to redo your fill plan over a stray fraction.
All calculations apply Dalton's Law of Partial Pressures with absolute-pressure END/EAD formulas, the same physics your dive computer uses, with no rounding shortcuts.
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.
Two modes, four screens. The same engine that powers Dive Kit's Deco Planner.
Nitrox
Set your max depth and PPO₂ limit (1.2 / 1.4 / 1.6 presets, or custom) and Dive Kit returns the highest oxygen fraction that stays safe, the richest mix for the most no-deco time. The result panel shows the recommended EAN, plus the gas at MOD: PPO₂, EAD, END, and gas density.
Trimix
Switch to Trimix mode and set your target Equivalent Narcotic Depth, Dive Kit adds just enough helium to keep narcosis in your comfort zone. Add an optional max gas density limit and helium will keep climbing if work-of-breathing demands it. Every input is bidirectionally coupled: depth, O₂%, He%, and END all recompute live.
More free dive planning tools in Dive Kit.
Download Dive Kit free on iOS and Android. Best Mix Calculator is included, no account, no ads, no internet required.