Scuba Nerd
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Scuba Nerd

Scuba Nerd, diving with knowledge.

Dive with knowledge

Planning · Gas · Decompression · Logbook

Scuba Nerd capabilities

  • Smart dive planning

    Plan recreational, technical open-circuit and CCR dives from one planner.

    OC + CCR

  • Smart OC Wizard

    Build an open-circuit dive from intent and constraints, not a blank form.

    9 steps

  • Decompression

    See the stops, the switches and the runtime behind the dive.

    TTS 51 min

  • ZHL-16C + gradient factors

    Bühlmann ZHL-16C, with the gradient factors you choose.

    GF 30/70

  • Technical open circuit

    Multi-gas dives with travel and deco gases and planned switches.

    19/50, EAN50, O2

  • CCR

    Diluent, setpoint schedule, and a bailout plan of its own.

    SP 0.7 / 1.3

  • Best Mix

    A mix for your ppO2, density and END limits.

    Tx19/50 at 60 m

  • Gas density

    Breathing-gas density at depth, against 5.2 and 6.2 g/L.

    5.18 g/L

  • END

    Equivalent narcotic depth, with the narcosis model stated.

    END 25 m

  • Lost gas contingency

    Each deco gas removed and re-planned through the same engine.

    EAN50 lost: +30 min

  • ICD

    Counterdiffusion screening on helium-to-nitrogen switches.

    Rule of fifths or halves

  • Gas calculators

    Nitrox, Trimix and EAD, with MOD, END and ppO2 at depth.

    MOD at 1.4 / 1.6

  • Gas laws

    Boyle, Charles, Gay-Lussac and Dalton, as calculators.

    P1V1 = P2V2

  • Dalton triangle

    Partial pressures for O2, N2 and He.

    PO2 = FO2 × Pabs

  • Dive logbook

    Cylinders, gases, events and notes in one structured record.

    Rec, Tech, CCR

  • Plan to log

    Start a log from the plan, then record what happened.

    Plan prefill

  • Printable plans

    A Dive Plan Report PDF, and a slate for the water.

    PDF + slate

  • Center sheet

    A one-page sign-off sheet for the dive operation.

    1 page

  • Know why

    Results arrive with the reasoning behind them.

    Why this mix?

  • Safety by visibility

    Assumptions, limits and contingencies stay in view.

    Ready or Calculated

  • Plan the dive.
  • Understand the gas.
  • See the decompression.
  • Know the contingencies.
  • Log what actually happened.
Open Scuba Nerd Explore the platform

Drag to turn the sphere

  • Plan the dive.
  • Understand the gas.
  • See the decompression.
  • Know the contingencies.
  • Log what actually happened.

More than a dive planner

Scuba Nerd brings dive planning, gas analysis, decompression, contingency thinking and logging into one connected workspace.

Whether the dive is recreational, technical open circuit or CCR, the goal is the same:

  • make the assumptions visible,
  • make the calculations understandable,
  • and keep the diver in control of the decisions.
Two choices, four kinds of plan
Plan typeOpen circuitCCR
Simple PlanOne depth and bottom timeSupportedSupported
Technical PlanMulti-level, deco gases, switchesSupportedSupported

One engine underneath: Bühlmann ZHL-16C with gradient factors, metric depths, salt or fresh water and your surface pressure.

Plan the whole dive

One plan holds the profile, the gases, the switches and the decompression, and every number stays attached to the assumptions that produced it.

  • Dive profile
  • Gas selection
  • Decompression
  • Gas switches
  • Runtime
  • Gradient factors
  • Environment
  • Gas density
  • END
  • Lost gas
  • ICD
Sample dive profile Descent to 60 metres in 3 minutes, 17 minutes at the bottom, then decompression stops from 27 metres to 3 metres with switches to EAN50 at 21 metres and oxygen at 6 metres, surfacing at 71 minutes.

0 min0 mTrimix 19/50

  1. Environment Salt water, 1.013 bar at the surface.
  2. Dive profile Descent to 60 m in 3 min.
  3. Gas selection Trimix 19/50: ppO2 1.33 at depth.
  4. Gas density 5.17 g/L at 60 m, under the 5.2 g/L preferred limit.
  5. END 25 m, oxygen counted as narcotic.
  6. Gradient factors GF 30/70: first stop at 27 m.
  7. Gas switch EAN50 at 21 m. ICD screening runs on this helium-to-nitrogen switch, as an advisory.
  8. Gas switch Oxygen at 6 m.
  9. Decompression 14 min at 3 m to finish.
  10. Runtime TTS 51 min, runtime 71 min. What if a gas is lost?
Runtime
DepthStopRunGasDone
60172019/50
2712619/50
2422919/50
21131EAN50
18234EAN50
15237EAN50
12341EAN50
9547EAN50
6149O2
6655O2
31470O2
0–71Surface

Sample output from the Scuba Nerd planner: 60 m for 20 min on Trimix 19/50 with EAN50 and oxygen, GF 30/70, salt water. CNS 39.5 %, OTU 79. Not a plan for your dive.

Start with the dive, not the form

Tell Scuba Nerd what you are trying to do.

The Smart OC Wizard helps turn the objective, depth, time, environment and gas constraints into a structured open-circuit plan.

Then the normal planner remains available for inspection and refinement.

Open Smart Wizard

Smart OC Wizard

  1. Depth & time60 m, 20 min, salt water
  2. Gas strategyHelium on, ppO2 1.40, END 30 m, O2 narcotic
  3. Bottom gasCandidates with ppO2, END and density
  4. ProfileSquare or multi-level
  5. Travel gasOnly if the bottom gas needs one
  6. Deco gasesSwitch depth and ppO2 for each
  7. SettingsGF, rates, last stop, ICD rule
  8. PreviewRuntime and lost-gas table
  9. Review & createSaved as an ordinary plan

Then choose Edit with Wizard or Manual Edit. The wizard plans open circuit only.

The best mix depends on the constraints

"Best Mix" is not one universal gas. It is the best result under the constraints you select, so change a constraint and see what happens.

Best Mix

Depth
60 m
Max ppO2
1.40
END
30 m
Gas density
Narcosis
Depth buffer

Result

Tx19/50

Limited by gas density

Why this mix?

ppO2
19 % oxygen, the richest whole percent under 1.40 at 60 m: ppO2 1.33.
Gas density
END
Environment
Salt water, 1.013 bar at the surface.

Outputs of Scuba Nerd's Best Mix engine for these inputs. None of them is a recommendation for your dive.

Plan for the dive that changes

Scuba Nerd recalculates each applicable open-circuit lost-gas scenario through the same planning engine, rather than estimating the answer separately. Where no valid alternate plan exists, it says so.

Lost deco gas contingency Planning aid only
ScenarioBase planEAN50 lostOxygen lost
TTS51 min81 min60 min
Change–+30 min+9 min
Continue on19/50, EAN50, O219/50, O219/50, EAN50

Same sample dive as the runtime above: 60 m for 20 min, GF 30/70. Each column is a full re-plan, not an estimate.

When the last deco gas goes

45 m, 30 min on EAN28, carrying EAN50 only

"Losing EAN50 leaves no deco gas: the diver would finish decompression on back gas only (new TTS 64 min, +21). Confirm the back gas is breathable at every stop and carry redundancy."

When no plan remains

"Losing EAN50 leaves no valid decompression plan with the remaining gases. Carry a redundant supply and review the dive."

The wording Scuba Nerd uses when a re-plan fails. Gas name for illustration.

Open circuit only, covering deco gases. The same table prints in the Dive Plan Report, on the Center Sheet and on the slate. CCR bailout is planned separately, below.

Open circuit is not the whole story

A rebreather plan is built around the loop: the diluent, the setpoints and the depths where they change.

Scuba Nerd computes CNS and OTU on the loop, and judges gas density and END on the loop mix rather than on the diluent label.

The bailout is its own plan: one scenario, at the end of the bottom phase where it is the worst case, with its own schedule, oxygen exposure and a supply table. When no staged gas is breathable at depth, Scuba Nerd says there is no open-circuit escape.

Not modelled: scrubber duration, cells, solenoid or work of breathing.

CCR, 60 m for 40 min

Diluent
Trimix 21/35
Setpoints
0.70, then 1.30 from 20 m down, 0.70 from 6 m up
Loop plan
TTS 130 min, CNS 61 %, OTU 163
Loop density
6.19 g/L at 60 m, above the 5.2 preferred limit

Bailout, end of bottom

On 21/35
"No bailout gas is breathable at 60 m." ppO2 1.47 is past its 1.40 limit.
On 18/45, EAN50
TTS 137 min, first stop 36 m, at 30 L/min
Gas needed
2,367 L of 18/45 and 5,541 L of EAN50
Supply
Unverified: no cylinders entered

Sample outputs from the Scuba Nerd planner, GF 30/70, salt water. Not a plan for your dive.

Understand the numbers

Every calculator in Scuba Nerd shows what it was calculated with. These are live today.

Calculators
CalculatorWorkingGives you
Best Mixrichest O2, least HeA mix for your ppO2, density and END limits
NitroxMOD = (ppO2 ÷ FO2 − 1) × 10MOD at 1.4 and 1.6, EAD, END, ppO2
TrimixEND = (D + 10) × (1 − FHe) − 10MOD, END, EAD, N2 content, ppO2
EAD(FN2 ÷ 0.79) × (D + 10) − 10Equivalent air depth, helium-aware
Dalton triangleP = F × PabsPartial pressure, fraction or depth for O2, N2, He
Boyle's lawP1V1 = P2V2Volume against pressure
Charles's lawV1 ÷ T1 = V2 ÷ T2Volume against temperature
Gay-Lussac's lawP1 ÷ T1 = P2 ÷ T2Cylinder pressure against temperature
SAC / RMV(P1 − P2) × V ÷ (t × Pabs)Your breathing rate in L/min and bar/min, from a guided test or a quick calculation

Nitrox, Trimix and EAD use 10 m per bar and 1 bar at the surface. Also in Scuba Nerd: gas blending, a gas library, weather and modeled sea level, and dive sites.

Try Dalton's law

Oxygen

ppO2 = FO2 × Pabs0.32 × 4.0 = 1.28

Within 1.4, the usual working limit.

A demonstration with 10 m per bar and 1 bar at the surface. Real planning happens in the app.

The plan is not the dive

Planning ends when the dive begins.

Scuba Nerd's logbook keeps the actual dive (profile and conditions, gases, cylinders, events, notes and sources) separate from what was originally planned. Convert to Log starts from the plan; you record what actually happened.

Plan

Depth
60 m
Bottom time
20 min
Runtime
71 min
Gases
Trimix 19/50, EAN50, oxygen
Settings
GF 30/70, salt water

Log

Max depth
60 m 58.6 m
Bottom time
20 min 22 min
Runtime
71 min 76 min
Gases
Trimix 19/50, EAN50, oxygen Planned
Events
Switch to EAN50 at 21 m, oxygen at 6 m
Notes
Current on the line at 9 m, extra time at 6 m.

An illustrative log. When you convert, Scuba Nerd shows: "The planned figures are shown for confirmation — record what actually happened."

Show the assumptions

  • No hidden gas model

    Calculators list what they were calculated with: surface pressure, water type, the density reference, 10 m per bar where it applies.

  • No hidden narcosis model

    Best Mix and the Smart OC Wizard ask whether oxygen counts as narcotic, and say which one they used.

  • No silent constraint relaxation

    When a limit cannot be met, the result says which one, instead of quietly loosening it.

  • No magic “safe” button

    A plan reads Ready only when its gas supply is verified. Otherwise it reads Calculated, or Cannot Be Dived.

Scuba Nerd is a planning and knowledge tool. The diver remains responsible for:

  • training
  • team planning
  • equipment
  • gas analysis
  • real conditions
  • and the final decision to dive.

Ready to plan?

Open Scuba Nerd

Planning · Gas · Decompression · Logbook

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What it does

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