Dive Plan vs Turn Pressure

Dive Plan is a dive planning and logbook app for recreational scuba divers. Plan single and repetitive no-decompression dives, work out Nitrox mixes, keep a complete logbook, and check the weather and water temperature at your dive site — all from your iPhone or iPad. PLAN YOUR DIVES • Plan first dives and repetitive dive chains using standard recreational no-decompression tables — pressure groups, no-decompression limits, and surface intervals • Repetitive dives carry each dive's pressure group into the next, with the surface interval pre-filled from real elapsed time • Clear safety-stop guidance (required or recommended) for every dive • The planner won't produce a dive that exceeds no-decompression limits — it tells you instead • Metric or imperial, switchable anytime NITROX / ENRICHED AIR • Set your oxygen fraction (FO2) and partial pressure limit (PPO2) • See maximum operating depth (MOD) and equivalent air depth (EAD) for each dive DIVE LOGBOOK • Record depth, bottom time, date and time, location, tank pressures, air/surface/bottom temperature, gas mix, and notes • Automatic, continuous dive numbering • Review your history on the dashboard: total dives, total bottom time, deepest and longest dives, plus today's dives and your last ten AT-A-GLANCE DASHBOARD • No-Fly countdown based on the DAN Flying After Diving guidelines — 12 hours after a single dive, 18 hours after multiple dives or consecutive days • Readiness: whether your next dive plans as a fresh first dive or a repetitive one, with a live surface-interval timer since your last logged dive • Current weather and sea-surface temperature for your location WEATHER & WATER CONDITIONS • Local forecast — current conditions, highs and lows, wind, and precipitation, powered by Apple Weather • Map view with search and dropped pins to check conditions anywhere • Sea-surface temperature from NOAA satellite data CERTIFICATIONS & CHECKLISTS • Keep your certification cards, with front and back photos, on your device • Build pre-dive and gear checklists and run them before every dive PRIVATE BY DESIGN • Your dives, logs, and photos stay on your device and in your own iCloud • No third-party analytics, no advertising, no tracking DESIGNED FOR IPHONE & IPAD • Universal app, all orientations • Light, dark, and system appearance, with optional background themes DIVE PLAN BASIC & PRO Dive Plan is free to use: one dive plan per day, a 20-entry logbook, one certification card, one checklist, and full weather access — free, forever. Upgrade to Pro for: • Unlimited dive planning • Repetitive dive planning with surface intervals • Nitrox / Enriched Air planning • Unlimited logbook entries, certification cards, and checklists • Premium background themes Pro is available as a monthly or annual subscription, or a one-time Lifetime purchase. Subscriptions renew automatically unless canceled at least 24 hours before the end of the period; manage or cancel anytime in your Apple Account settings. Payment is charged to your Apple Account on confirmation. IMPORTANT Dive Plan is a planning aid, not a substitute for proper training, a certified instructor, or a dive computer. Always dive within the limits of your training and certification, verify every plan against your own dive tables and dive computer, and never rely on a single tool. Calculated results are estimates. You are responsible for your own safety in the water. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

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.