Turn Pressure

Most recreational divers never plan their gas. They surface on 50 bar because that is the habit — and the habit does not change with depth, or cylinder, or who they are diving with.

Turn Pressure does that arithmetic. Tell it how deep, what you are carrying and what you breathe, and it gives you the pressure to turn on, the gas you have to keep back to get two people up, and how long you can stay.

What it does

• Minimum gas computed for your depth and your cylinder — the same ascent needs 84 bar from a 15-litre and 113 from an aluminium 80.
• Turn pressure on thirds, halves or all-usable.
• Bottom-time limit from Bühlmann ZH-L16C, for air and every nitrox mix, with the gradient factors set to match your computer.
• Your own air number, worked out from your own dives and tracked over time.
• Metric and imperial, in the numbers each is actually dived in — 100 ft and AL80, not 98 ft and "81 cu ft".
• Saved briefs for the dives you do often.

What it does not do

No account. No ads. No analytics. No network access at all — everything stays on your phone.

Your training comes first. In the water, go by your pressure gauge and your computer. This app helps with the mathematics and accepts no liability for any dive.