Turn Pressure – Dive Planner

Most divers were taught one number: surface on 50 bar, or 500 psi, no matter the depth, the cylinder, or who they're diving with. It's not that nobody plans — it's that the plan never changes with the dive. Turn Pressure runs the actual numbers instead. Tell it how deep you're going, what you're carrying and who's breathing it, and it gives you a turn pressure, the minimum gas to get two divers up from the deepest point, and a bottom time — before you kit up. It's a no-stop, recreational planner. It doesn't plan decompression dives, stage gases or bailout, and it isn't meant to run during the dive — plan with it on the boat or the night before, then go by your gauge and your computer in the water. WHAT MAKES IT DIFFERENT Minimum gas that scales. Most calculators hand you a flat reserve. Turn Pressure works from the volume two divers need to reach the surface, for your cylinder and your SCR — at 20 L/min, the same ascent from 30 m needs 45 bar from a 15-litre steel and 61 bar from an aluminium 80. Same dive, same divers, different tank, different number. A bottom-time limit for your gas, not just your air. Full Bühlmann ZH-L16C no-stop calculation for air, EAN28, EAN32 and EAN36, with gradient-factor presets from 30/70 to 100/100 — including 15/85 — defaulting to 40/85, so you can match whatever your computer is set to. Repeat dives use the dive you actually did. Tell it how deep you went and how long you were down, and it works out what nitrogen is still in you across your surface interval — instead of guessing at a dive it cannot see. If you don't tell it, it doesn't guess: it shows you nothing and says why. Two deep segments before the ascent. Deep first, then shallower — or the other way — and the gas, the turn pressure and the no-stop limit are planned across both, with minimum gas for each segment. An ascent you can brief. The way up is a ladder of levels — each with its own time and depth, labelled on the chart, with the gauge you leave it on — each a depth to hold or be shallower than. When the no-stop limit ends the deep part of a dive, the plan spends the remaining gas on the way up instead of sending you up with a full-looking gauge. One number, not two. Bottom time is whichever runs out first — your gas or your no-stop limit — and Turn Pressure tells you which one it was, so you know if you're gas-limited or NDL-limited before you're in the water. Your SCR (SAC), not an average off a chart. Type your own number, start from a tier, or work it out from one real dive's numbers — depth, time, cylinder, start and finish pressure. Turn Pressure keeps it as a dated list with a trend chart so you can watch it improve. Metric and imperial done properly. 100 ft and 130 ft, AL80 and HP100 — the numbers each system is actually dived in, not arithmetic conversions like 98 ft or "81 cu ft." EVERYTHING ELSE • Turn pressure on thirds, halves or all-usable gas • Single, or double/sidemount — 10 L and 12 L steel, aluminium 80, 15 L steel • Maximum operating depth for every mix, hard-blocked at ppO2 1.4; planning to 40 m, sea level only • Ascent rate you choose, 3 to 9 m/min — the reserve follows it and never shrinks • Two ascent profiles: NDL with a safety stop (a stepped ascent with 3 minutes at 5 m), or the Minimum Decompression Profile — 9 m/min to half your depth or 9 m, then 3 m/min, no stops — whose bottom times come from a published recreational schedule rather than from the model, and which plans EAN32 to 30 m because that is what the schedule covers • Saved briefs for the dives you run over and over • Share the plan as one picture — profile, bars per depth, minimum gas • Works with no signal, on any boat, anywhere Free. No account, no ads, no analytics, no network access at all — nothing leaves your phone. This is a planning tool, not a dive computer and not a decompression planner. Your training, your gauge and your computer decide the dive. Turn Pressure just does the arithmetic beforehand.