What Are Single-Gas and Multi-Gas Computers?
A single-gas dive computer lets you set one breathing mix per dive — either air (21% oxygen) or a single nitrox blend (typically 28–40% oxygen). The algorithm tracks your decompression status based on that one mix throughout the entire dive.
A multi-gas computer lets you program two or more gas mixes and switch between them during a dive. When you switch to a richer decompression gas at a shallower depth, the computer recalculates your deco obligations based on the new mix, typically shortening required stop times.
When Single-Gas Is All You Need
If you do any of the following, a single-gas computer covers every scenario you will encounter:
Recreational no-decompression diving — open water, reef, wreck penetration within recreational limits (40 meters max). You dive on air or one nitrox mix, stay within NDL, and ascend with a safety stop. This is how the vast majority of dives worldwide are conducted.
Single-mix nitrox diving — you fill your tank with one enriched blend (commonly EANx32 or EANx36) and dive the entire profile on that mix.
Every budget and mid-range computer supports at least one nitrox mix. The Cressi Leonardo 2.0, Mares Puck 4, Suunto Zoop Novo, and Shearwater Peregrine all handle single-gas nitrox diving perfectly.
Mares Puck 4
Simple, reliable, now with Bühlmann algorithm and Bluetooth. Handles air and nitrox.
When You Need Multi-Gas
Multi-gas capability becomes necessary when you carry and switch between different breathing mixes during a single dive. This applies to:
Decompression diving: You dive on a back-gas (air or trimix) and carry a richer nitrox or pure oxygen for decompression stops. The computer needs to track both mixes and recalculate deco obligations when you switch.
Technical diving: Multi-mix profiles with trimix (helium blends) for depth, travel gas for intermediate depths, and deco gas for stops. Computers like the Shearwater Perdix 2 support up to five gases including trimix.
Stage/bailout diving: Sidemount or rebreather divers who carry bailout bottles with different mixes.
The key point: multi-gas is not about having a "better" computer. It is a specific capability for a specific type of diving that requires specific training (typically TDI/PADI Tec or equivalent).
Shearwater Perdix 2
Up to 5 gas mixes, full trimix and CCR support, Bühlmann with adjustable GFs.
How Many Gases Do Computers Support?
| Gas Support | Typical Models | Best For |
|---|---|---|
| 1 gas (air + 1 nitrox) | Cressi Leonardo 2.0, Mares Puck 4, Aqualung i100 | Recreational no-deco |
| 2–3 gases (nitrox) | Suunto Zoop Novo, Peregrine/TX, Garmin G1 | Rec nitrox, intro deco |
| 3–5 gases (nitrox + trimix) | Perdix 2, Teric, Mk3i, EON Core | Full tech/deco diving |
| 5+ gases + CCR | Perdix 2, Teric, Mk3i (with CCR mode) | Rebreather diving |
The Future-Proofing Question
A common question: should I buy a multi-gas computer now even though I only dive recreationally, just in case I get into tech diving later?
Our take: no. Multi-gas computers cost more, and if you do progress into technical diving, you will likely want the specific computer your tech instructor recommends (almost always a Shearwater Perdix or Teric). Spending extra now on multi-gas capability you do not need means less money available for the actual tech training, courses, and equipment that define your progression.
Buy the right computer for your current diving. Upgrade when your skills demand it.
Shearwater Peregrine
The ideal recreational computer — no multi-gas cost premium, still Bühlmann with GFs.
Bottom Line
If you dive recreationally on air or a single nitrox mix, a single-gas computer does everything you need. Multi-gas is a technical diving feature — do not pay for it until you are trained to use it.