Contents

Deco engine

MultiDeco test results

Pick a scenario and compare the Dive Kit deco engine against the MultiDeco mobile app, side by side. MultiDeco is a mature planner that many divers trust, and we use it as a second opinion rather than an answer key. Every scenario behind the how Dive Kit compares to MultiDeco write-up is published here in full, so you can check the numbers yourself.

We compare against the MultiDeco mobile app (iOS and Android), the planner many technical divers already trust. Every MultiDeco number here comes from that mobile app. We have not tested the desktop version, so we make no claims about it. Identical numbers are not the goal: two correct engines differ a little on the judgment calls, so the aim is to agree on the physics that matters and to explain every difference. To line the two up, the Dive Kit column runs in rounded mode (whole-minute stops) for every scenario, since MultiDeco shows whole minutes too. We publish each scenario's inputs, MultiDeco's output and Dive Kit's output below, and the same scenarios run in our automated test suite, so the numbers cannot drift without us catching it.

S1

Air 30 m / 23 min, GF 30/70 (salt)

Decozone within 1 deco step O₂ clock matches
Open this plan in Dive Kit

Generated with Dive Kit v2.8.2. The link loads the exact inputs, so the app reproduces the table you see here. A later app version may shift a number slightly; we keep these pages current when we can.

The dive

one dive · two planners

30 m × 23 min · Air

Gradient factors
30/70
Water
Salt
Last stop
3 m
Gases
Air
▸ How each app was configured

MultiDeco

  • Bottom time entered 25 min (descent-inclusive)
  • Ascent 9/6/3 m/min (deep/deco/surface)
  • Bottom gas pinned per profile step; deco gases listed separately

Dive Kit

  • At-depth bottom time (descent counted separately)
  • Two-rate ascent 9/3 m/min, switching at 3 m
  • Profile + gas list kept separate; deco gas auto-selected by MOD

Same physical dive, entered in each tool's native style. That is why a few numbers are distributed differently while the physics agrees.

Metric MultiDeco Dive Kit Δ Agreement
Decozone start (m) 21 20.7 -0.3 match
First stop (m) 12 12 0 match
Time to surface (min) 22 24 +2 match
CNS (%) 6 6 0 conservative
OTU 18 17.9 -0.1 match
Gas density (g/L) 4.8 5.17 +0.37 conservative

A ✓ means within the documented tolerance for that metric. “≈” marks a deliberate, explained difference (e.g. stop distribution, or Dive Kit's more-conservative O₂ clock). See the shared explanations below; it is never an error.

▸ Full stop-by-stop schedules

MultiDeco

DepthStopRunGas
12 m1min2821
9 m3min3121
6 m4min3521
3 m11min4621

Dive Kit

DepthStopRunGas
12 m3min3021
9 m4min3421
6 m6min4121
3 m7min4821

Why they differ

A clean match. The differences here are the usual documented conventions (stop distribution and the gas-density reference offset). See the shared explanations.

The differences, explained once

Every per-scenario note in the viewer points back to one of these shared explanations.

Ascent-rate match We run Dive Kit at the same ascent speeds we used in MultiDeco, so the comparison is fair. The deep speed that sets the first stop is 9 m/min in both.

Dive Kit and MultiDeco climb at the same speeds in these runs. The speed that decides where your first stop lands is the deep ascent, from the bottom up to the first stop, and that is 9 m/min in both tools, so that part is a like-for-like comparison. On the S and FS dives, MultiDeco moves a little slower between the shallower stops (6 m/min) than Dive Kit does, but that does not change where the first stop lands. We tested this directly: the difference in the first stop stays the same when we match the deep speed, so it comes from how Dive Kit recomputes your tissues while you climb, not from climbing faster or slower (see general/stopDistribution).

Decozone start Decozone start is GF-independent by design and matches MultiDeco within about one deco step on every scenario except the deep multi-level P1, where it reads ~10 m shallower — a definition difference, not a model error.

Dive Kit computes a 'decozone start', the depth where your decompression obligation begins. We use it here as a clean cross-check; it is not shown in the app. It is the deepest depth where a tissue's total inert-gas pressure (nitrogen plus helium) passes the surrounding pressure, and it does not depend on your gradient factors, because gradient factors move the M-value line, not the ambient line. You can see this in the data: S2 (GF 30/70) and S7 (GF 50/80) are the same 45 m / 22 min air dive and both show about 32 m, even though their first stops differ (21 vs 15 m). Across the 26 scenarios Dive Kit lands within about one 3 m step of MultiDeco (at most 3.6 m, on the deepest high-helium CCR dive, C3) — with one exception, the deep multi-level dive P1 (35 m vs 45 m). There Dive Kit computes the decozone from the end-of-bottom tissue state, after the shallow second level (42 m) off-gasses the fast compartments, while MultiDeco appears to use the deepest-point value; that is a definition difference on a multi-level profile, and the operational first stop still matches at 27 m (see P1).

Stop distribution Dive Kit's first stop can be shallower than MultiDeco's. The total decompression is the same; it just sits at different depths.

MultiDeco lists a short stop at almost every 3 m step from the deepest stop up, often well under a minute. Dive Kit holds fewer, longer stops and skips the deepest ones, so its first listed stop is shallower (S6: 36 vs 48 m; S5: 27 vs 33; FS5: 21 vs 27). Both tools agree on the deepest depth where you owe a stop. They differ on the way up: Dive Kit recomputes all your tissues every second as you climb, the way the computer on your wrist does, so it counts the gas you breathe off during the climb itself. Helium leaves the fast tissues quickly, so on a helium dive the ceiling drops faster than you climb, and there is nothing to stop for in those first few metres. The gap is biggest on deep, high-helium dives (12 m on S6, 6 m on S5 and FS5) and at most one 3 m step on air and nitrox. The total time to surface stays within a minute or two either way (S6 82.6 vs 81, S5 45.3 vs 45, FS5 40.2 vs 42, A2 55.4 vs 56), and Dive Kit's leading tissue still reaches the surface exactly at your GF-High, so it never shortcuts your decompression. Compare total time to surface, not the depth of the first stop. The one exception is a dive with a long 6 m last stop, where Dive Kit finishes a few minutes sooner (see A4 and A5).

CNS basis (ambient ppO₂) Dive Kit uses ambient ppO2 for CNS (the more conservative, NOAA/Baker-aligned choice).

CNS oxygen-toxicity % is accumulated against the NOAA exposure limits using the AMBIENT ppO2 (fO2 x absolute pressure), with no alveolar water-vapour subtraction. This is Erik Baker's published method and matches Shearwater, Garmin and Subsurface; it is slightly more conservative than a water-vapour-reduced value. It runs ~1-3% higher than MultiDeco on most dives, and noticeably higher when a high-ppO2 deco gas sits right at a steep bracket of the NOAA curve (see S6).

Gas-switch caps Each gas switches at a depth set by its oxygen content (caps 1.4/1.5/1.6 bar). These match MultiDeco's switches within one stop.

Dive Kit caps each gas by its oxygen content: a lean mix (under 28% oxygen) at 1.4 bar, a mid mix (28 to 45%) at 1.5, a rich mix (45% or more) at 1.6. The same cap sets both the switch depth and the hyperoxia warning. MultiDeco caps gases the same way, so at its default 1.4/1.5/1.6 every gas switch in these scenarios matches within one 3 m stop: Tx21/35 at 54 vs 57 m, Tx35/25 at 30 vs 33 m, and EAN50 (21 m) and oxygen (6 m) exactly. The small differences are only which 3 m stop the switch lands on.

Gas density Small gas-density offset (~7-9%) from differing gas-temperature assumptions.

Dive Kit's worst-case gas density (e.g. S1 air at 30 m ~5.2 g/L) runs slightly above MultiDeco's (4.8 g/L) because the two tools assume different gas temperatures in the ideal-gas density calculation. Both flag the same density warning thresholds; the absolute number is a reference, not a safety boundary.

Gas usage (litres) Litres used depend on your breathing rate, so this is not a comparison of the deco math.

Gas consumption depends entirely on the breathing-rate (RMV/SAC) settings, which are a user preference, not a deco-model output. Dive Kit's figures here use RMV 20 (working) / 15 (deco) L/min, so absolute litres differ from a MultiDeco run configured with a different SAC. Match the SACs before comparing litres.

CCR loop deco CCR (rebreather) loop deco matches MultiDeco closely. CNS and OTU are near-exact, decozone within a step.

Pure-loop CCR deco (constant setpoint 1.3, no open-circuit switches) holds up well across air, trimix and deep high-helium diluents (C1 to C3): CNS within 1 percentage point (27/27, 37.8/37, 53.9/53), OTU within 2 to 3 units (71.8/70, 100.5/99, 143.4/140), and time to surface within 1 to 3 min. Decozone is within one 3 m step except on the deep 80 m high-helium dive C3 (65.6 vs 62, the same wider spread seen on the deep trimix dive S6). The first listed stop is shallower than MultiDeco, the usual stop-distribution effect on a helium diluent (see general/stopDistribution). Gas density runs about 8% higher (temperature assumption). CCR is also covered by our automated tests.

Run it yourself

You don't have to take our word for any of it. Enter these exact scenarios in Dive Kit and in the MultiDeco mobile app and compare them against the numbers above. We publish the full data set here: every scenario's inputs, both tools' outputs, and the per-scenario notes. Both columns show whole-minute stops, because the Dive Kit column runs in rounded mode, which is the app's default.

Join the four files by scenario id. The Dive Kit engine is proprietary, but every output here is reproducible by running the same dive in the app. The comparison stands on the data, not on trust.

The full write-up covers how the cross-check is run, where the two planners agree and differ, and a step-by-step trace of the deep-stop difference: see How Dive Kit compares to MultiDeco.

Parts of this guide were drafted with AI assistance and may contain mistakes. It's educational, not a substitute for training. Always dive within your certification and verify with your instruments.