Time to Surface

Staged decompression from 15 to 51 metres — deeper to 56 with a warning — on six bottom gases, with one deco bottle. Runtime, stops, minimum gas and both cylinder fills, before you kit up. Free. No in-app purchases, no subscription, no account. WHAT IT PLANS • Staged decompression, 15 m to 51 m. Past 51 m it plans and warns rather than refuses — there gas density binds before oxygen does • Six bottom gases: EAN32, triox 30/30, EAN28, air, 21/35 and 18/45 • One decompression gas — EAN50 or oxygen — in an AL80, AL50 or AL40 • Twin cylinders on the back, yours to pick • Bühlmann ZH-L16C, gradient factors yours to set, 20/85 by default • ppO2 1.2 bar working and 1.6 bar at a stop by default — stricter than the 1.4 most divers trained at. Both adjustable • Descent 10 m/min, 9 m/min to the first stop, 3 m/min between stops, and the last 6 m at 1 m/min. Stops every 3 m with the last at 6 m. All four rates adjustable • Metric or imperial THE GAS PLAN Back gas fill and turn pressure on thirds, halves or all usable. Minimum gas — what two divers on one back-gas supply need to leave the deepest point and reach the surface, at the minimum ascent rate rather than the planned one. Deco bottle fill and reserve. CNS. Every stop, every travel leg and the slow last six metres is charged against the fill you entered, level by level, from the schedule that was actually solved. And it says which of the three ends the dive — your back gas, your deco bottle or your CNS clock — and at which minute. THE DIVE, MINUTE BY MINUTE Every leg carries the runtime it starts at and the runtime it ends at, so you can see where each line begins and ends without doing arithmetic. One tap lays the whole plan out as a wetnote page — schedule, gas checkpoints and contingencies — sized to copy by hand. DIVES BEFORE THIS ONE Keep a plan under a name, then say that up to three of them came before the one you are planning, each with the surface interval before it. Nitrogen and helium both cross the interval, and CNS decays at a 90-minute half-time. No published table covers repetitive decompression dives; this runs your own previous profiles through the same model. CONTINGENCIES, SOLVED Lose the deco bottle, add five minutes on the bottom, or go three metres deeper — each one re-solved through the same model, not scaled by a rule of thumb. If your cylinders will not fund a contingency, it says so. PRAGMATIC DECOMPRESSION Off by default. Switched on, it linearises the stops between 21 m and 9 m into one flat time per rung and re-solves the last stop from there — a simpler profile to run in the water, not a more conservative one. The unadjusted profile is what the app computes otherwise. WHAT IT DOES NOT PLAN Closed-circuit rebreathers. Cave or wreck penetration. Hypoxic mixes and travel gas. More than one decompression gas. Altitude — sea level only. It does not compute OTU. One decompression gas per dive is a stated limit of this release, not an oversight. If your plan calls for two bottles, this is not your planner yet. INSIDE ITS ENVELOPE, IT REFUSES RATHER THAN WARNS A gas past its oxygen limit, an exposure past the maximum, cylinders that will not cover the plan, a surface interval under an hour — all produce no numbers at all, rather than a number with a caution attached. YOUR DIVE COMPUTER OWNS THE DIVE This is pre-dive arithmetic. It never pronounces a dive safe, and it is not a substitute for training, for your computer, or for your own judgement in the water. Offline. No ads, no analytics, no tracking. Nothing leaves your phone. iPhone, iOS 17 and later. Questions and bug reports: timetosurface@ismailov.net