The three dominant decompression algorithms in recreational and technical diving each take a fundamentally different approach to modeling gas uptake and elimination. This comparison lays them side by side so you can understand what your dive computer is actually doing — and why two divers at the same depth may get different no-decompression limits.
Quick Overview
| Feature | Bühlmann ZHL-16C | RGBM | VPM-B |
|---|---|---|---|
| Developer | Albert Bühlmann | Bruce Wienke | David Yount |
| Model basis | Dissolved gas only | Dissolved gas + microbubbles | Bubble nuclei permeability |
| Transparency | Fully published | Proprietary implementation | Published theory, closed implementation |
| User control | Gradient factors (fully adjustable) | Conservatism levels (limited) | Conservatism settings (varies) |
| Used by | Shearwater, Ratio, some Garmin | Suunto, Mares | Tech diving software, some Shearwater |
| Repetitive dive penalty | Standard tissue loading | Aggressive cumulative penalty | Moderate |
| Deco stop strategy | Shallower stops, longer shallow | Varies by implementation | Deeper stops, shorter shallow |
For Recreational Divers
On a single recreational dive to 60–80 feet, all three algorithms produce similar no-decompression limits — within a few minutes of each other. The difference you notice in practice is usually the conservatism setting, not the algorithm itself. A Suunto on "high" conservatism will give shorter NDLs than a Shearwater on GF 45/95, regardless of the underlying math.
Where algorithms diverge is on repetitive dives and multi-day diving. RGBM applies cumulative penalties that reduce your NDL on the third and fourth dives of the day more aggressively than Bühlmann. If you're doing four-dive days on a liveaboard, you'll notice RGBM cutting your bottom time on later dives.
For Technical Divers
Technical divers overwhelmingly use Bühlmann with gradient factors because the math is open, verifiable, and tunable. You can set GF 30/70 for conservative decompression or GF 45/85 for a more standard profile, and the resulting schedules can be cross-checked against desktop planning software. This transparency is essential when dive plans involve multiple gases, extended decompression, and real consequences for errors.
VPM-B has a technical following because its deeper-stop strategy intuitively appeals to divers who believe stopping deeper reduces bubble formation. The empirical evidence for this is mixed — some research suggests deeper stops increase overall inert gas loading, which could be counterproductive.
The Bottom Line
For recreational divers: pick the computer that fits your wrist, your budget, and your preferred brand. The algorithm will keep you safe as long as you follow it. For technical divers: Bühlmann with gradient factors offers the most control, transparency, and verification capability.