Your Dive Computer Runs
Bühlmann ZHL-16C.
Your Planner Should Too.
The only browser-based dive planner verified at Δ=0 against Shearwater, Garmin, and Suunto. Same algorithm. Same NDLs. Same ceilings. Stop wondering why your planning software and your wrist computer disagree.
From the First Reef Dive to 250ft Trimix Wrecks
DiveCommand scales with your diving. Whether you’re planning a straightforward 60ft recreational dive or a multi-gas technical profile with decompression obligations, the same 16-compartment engine handles it.
Why Your Planning Software and Your Dive Computer Disagree
Most dive planning software uses outdated algorithms or approximate implementations of Bühlmann. Your Shearwater doesn’t. Here’s where the gaps come from.
Generic planners use mathematical approximations of the Bühlmann model — close enough for marketing copy, wrong enough to produce different NDLs and ceilings than your actual dive computer. DiveCommand uses the exact ZHL-16C implementation at the exact GF values (40/85) that Shearwater, Garmin, and Suunto ship with. The numbers match because the math is identical.
Planning a dive in Lake Tahoe at 6,225ft without altitude correction gives you dangerously optimistic NDLs. The reduced atmospheric pressure at altitude changes every calculation — surface pressure, tissue saturation, NDL, ceiling depth. DiveCommand handles all of it automatically. Select your elevation, and every NDL, ppO₂, and decompression obligation recalculates instantly.
Most technical dive planning software looks like it was built in 1995. Desktop-only installs, clunky interfaces, no dynamic tissue feedback as you build the plan. DiveCommand runs in any browser, works completely offline, and recalculates all 16 tissue compartments in real time as you change depth, gas, or gradient factors. No installation. No waiting. No learning curve.
Watch Your Body Respond
to Every Change.
Select depth and gas. DiveCommand immediately returns your NDL, ppO₂, and CNS O₂ — calculated across all 16 Bühlmann ZHL-16C tissue compartments simultaneously. The tissue bars update in real time as you change any parameter.
Adjust your gradient factors. The tissue ceilings shift. Change from air to EAN32. The NDL extends and ppO₂ updates. Switch to trimix for a deep technical profile. The EAD, END, ENP, and Z-factor real gas values recalculate instantly. This is what it looks like when planning software actually models what your body is doing.
The Δ=0 badge isn’t marketing. It’s the result of a Python reference implementation written from scratch — separately from the JavaScript engine — that produced identical results at every depth and gas combination tested. 12,067 independent tests. Zero failures. Zero discrepancies.
If Your Computer Runs It, DiveCommand Matches It
Bühlmann ZHL-16C at GF 40/85 is the factory default on every major dive computer. DiveCommand uses the same constants, the same compartment half-times, the same gradient factor implementation.
Δ=0 means zero deviation in NDL and decompression ceiling at factory default GF settings. Verified using an independent Python reference implementation with separate codebase — not self-comparison. The validation harness is a public self-contained HTML file. Open it in any browser and run the tests yourself.
No More Manual
Altitude Conversion Tables.
At 6,225 feet above sea level, Lake Tahoe’s reduced atmospheric pressure changes every calculation a diver makes. The standard sea-level NDL for 60ft is 55 minutes. At Tahoe altitude, that NDL is shorter — and anyone planning without correction is operating on the wrong numbers.
DiveCommand’s altitude correction is built in, not bolted on. Select your surface elevation and every NDL, ppO₂, EAD, and decompression obligation recalculates automatically — no conversion tables, no manual offsets, no hoping you did the math right on the boat deck at 5am.
Lake Tahoe 6,225ft is a one-tap preset. Full altitude table covers sea level through 11,000ft in standard increments.
Built-In (ft)
Correction (ft)
@ Tahoe Elevation
On Elevation Select
Everything From a Reef Dive to a 330ft Trimix Profile
DiveCommand scales from a single recreational no-stop dive to a multi-gas technical decompression profile. The same validated engine handles both.
All 16 Bühlmann tissue compartments running simultaneously — 5-minute fast tissues to 635-minute slow tissues. GF 40/85 factory defaults match Shearwater, Garmin, and Suunto exactly. Adjust GF Low and GF High independently for custom conservatism profiles. Tissue bars update in real time as you change any parameter.
✓ Δ=0 · ZHL-16C · GF 40/85Full technical gas planning to 330 feet. EAD (Equivalent Air Depth), END (Equivalent Narcotic Depth), ENP (Equivalent Narcotic Pressure), and Z-factor real gas corrections for high-pressure helium mixtures. Custom gradient factor presets for different profile types. Three-bottle stage/deco gas management with rock bottom gas calculator.
✓ Trimix · EAD · END · ENP · Z-factorSea level through 11,000ft in standard increments. Lake Tahoe 6,225ft one-tap preset. Every NDL, ppO₂, EAD, END, and decompression ceiling recalculates automatically on elevation change. The altitude correction isn’t a lookup table — it’s integrated into the core ZHL-16C calculation so every tissue compartment reflects the correct ambient pressure.
✓ Auto-Corrected · Tahoe PresetToggle between Air, EAN32, EAN36, or any custom nitrox or trimix blend and watch ppO₂ thresholds, MOD, CNS O₂ percentage, and tissue loading update simultaneously. ppO₂ hard limit enforcement at 1.4 and 1.6 ata. CNS clock tracks cumulative oxygen toxicity across the dive. Visual warnings before any limit is approached.
✓ ppO₂ · MOD · CNS O₂ · LiveLog every dive with site name, buddy, maximum depth, bottom time, gas mix, water temperature, and visibility. SAC rate tracking lets you compare gas consumption across dives and conditions. Plan vs actual comparison shows how your real dive differed from the planned profile. Full CSV export for your records or training review.
✓ SAC Rate · Plan vs Actual · CSVLiveaboard planning across an expedition dive trip. Surface interval nitrogen credit and tissue loading carry forward from dive to dive across multiple days. The tissue state at the end of Dive 4 on Day 2 is the starting point for Dive 1 on Day 3. No manual resetting between days — the model tracks your body’s actual nitrogen load continuously.
✓ Multi-Day · Expedition PlanningGenerate a clean, print-ready dive plan showing profile, NDLs, gas switches, CNS budget, and decompression schedule. SVG dive profile visualization shows depth vs time with tissue compartment loading overlay. Bring a printed plan to the boat, hand it to your buddy, clip it to your slate — it’s fully self-contained without internet access to view.
✓ SVG Profile · Print-ReadyFreshwater is less dense than saltwater — 33ft of seawater equals 34ft of freshwater to reach the same pressure. A 100ft freshwater dive has different ATA, different ppO₂, different EAD, and slightly different tissue loading than a 100ft saltwater dive. DiveCommand corrects all of it automatically when you flip the toggle. Verified to match the physics formula exactly across all 11 test depths.
✓ SW / FW Density CorrectedInstall once in any browser. No app store. No account. No download. Once loaded, DiveCommand runs completely offline — iOS, Android, Mac, Windows, tablet, phone. Remote dive boat with no signal? Mountain lake with no WiFi? Plan the profile, run the numbers, print the plan. Everything works with zero connection.
✓ Any Device · Offline-FirstValidated by an Independent Reference Implementation
DiveCommand’s ZHL-16C engine was validated using a Python reference implementation written entirely from scratch — separate codebase, same Bühlmann 1990 constants, no shared code with the JavaScript engine. Both implementations were tested across 12,067 independent cases spanning every depth, gas mix, and gradient factor combination in the test suite. Agreement at Δ=0 at every case confirms the JavaScript engine correctly implements the mathematical model. The validation harness is a self-contained HTML file — open it in any browser, run the tests, verify the results yourself.
What Approximation-Based Planners Miss
Most online dive planners use simplified formulas rather than the full Bühlmann model. Here’s what you get when the algorithm is exact.
| Capability | DiveCommand $149 lifetime |
Generic Planners Free / Various |
|---|---|---|
| Full Bühlmann ZHL-16C algorithm | ✓ | Approximate |
| GF 40/85 factory default — matches wrist computers | ✓ | — |
| Δ=0 verified vs Shearwater · Garmin · Suunto | ✓ | — |
| All 16 tissue compartments tracked simultaneously | ✓ | Rarely |
| Custom GF Low / GF High adjustment | ✓ | Sometimes |
| Trimix to 330ft · EAD · END · ENP · Z-factor | ✓ | Rarely |
| Rock bottom gas calculator | ✓ | — |
| 3-bottle stage/deco gas management | ✓ | — |
| Altitude corrections — sea level to 11,000ft | ✓ | Rarely |
| Freshwater / saltwater density toggle | ✓ | — |
| ppO₂ · MOD · CNS O₂ live tracking | ✓ | Some |
| SVG dive profile visualization | ✓ | Some |
| Integrated logbook · SAC rate · plan vs actual | ✓ | Some |
| Multi-day nitrogen carry-over | ✓ | — |
| CSV export for all logged dives | ✓ | Rarely |
| 100% offline · any device · no download | ✓ | Varies |
| Independent validation harness (public) | ✓ | — |
| Lifetime license — no subscription | ✓ | Freemium |
Runs Offline. Works Anywhere.
Remote dive boat with no cellular. Mountain lake with no WiFi. Live-aboard in the middle of the Pacific. DiveCommand installs once and runs completely offline from that point forward — iOS, Android, Mac, Windows, tablet, or phone. Every tissue compartment calculation, every altitude correction, every logbook entry, every printed dive plan works without a connection. A world-class decompression model that fits in your pocket and doesn’t need the internet to think.
Own Your Software. Own Your Profile.
Skip the recurring app store charges. Buy it once, use it forever. All future updates included.
Bühlmann ZHL-16C · Single User · Any Device
- ✓ Full Bühlmann ZHL-16C engine — GF 40/85 factory default
- ✓ Δ=0 verified against Shearwater, Garmin, and Suunto
- ✓ 16-compartment tissue tracking — live recalculation
- ✓ Custom GF Low / GF High gradient factor adjustment
- ✓ Technical mode: trimix to 330ft, EAD, END, ENP, Z-factor real gas
- ✓ 3-bottle stage/deco gas management + rock bottom calculator
- ✓ ppO₂ · MOD · CNS O₂ tracking with live safety thresholds
- ✓ Altitude corrections — sea level to 11,000ft, Lake Tahoe preset
- ✓ Freshwater / saltwater density toggle
- ✓ SVG dive profile visualization · print-ready dive plans
- ✓ Integrated logbook — site, buddy, SAC rate, plan vs actual
- ✓ Multi-day expedition nitrogen carry-over
- ✓ CSV export for all logged dives
- ✓ 100% offline · any device · no download or account required
- ✓ All future updates included — no version upgrades to purchase
Written by a Diver, Not a Developer Who Read About It
Scott Fontecchio is a PADI Master Scuba Diver Trainer and SSI Master Instructor with 40+ years of diving experience at Lake Tahoe and beyond. He’s worked at altitude on Tahoe’s high-desert lake for decades and felt the specific frustration of planning tools that don’t account for elevation correctly, or that produce different numbers than the computers students strap on their wrists.
DiveCommand was built because he was tired of explaining to students why the planning software said one thing and their Shearwater said another. The Δ=0 verification isn’t a marketing claim — it’s the result of building a separate Python implementation from the same Bühlmann 1990 source, running 12,067 test cases, and confirming zero deviation at every single one. The math is the same because the same math was used.
The validation harness is public. Load it in a browser and run all the tests yourself. Then plan your last dive in DiveCommand and check the NDLs against your computer. That’s the whole pitch.
See the Δ=0 Difference
For Yourself.
Input your favourite dive profile. Check the tissue compartments. Match it against your personal dive computer. When the numbers are identical, you’ll understand why this matters — and why you’d rather plan this way than any other.
✓ Any Device · Works Offline ✓ All Future Updates Included ✓ Δ=0 vs Shearwater · Garmin · Suunto