Choosing a dive computer.

A model, not a guarantee

Your training and your instructor come first: reading a computer, planning with it and responding to its warnings are taught on a course. The agency, maker and medical sources below make the same point about limits:

• PADI's blog (Megan Denny, 2026) says a computer cannot account for age, fitness or alcohol, and quotes DAN that algorithms give guidance, not guarantees.
• Suunto, a computer maker, states that all decompression models are theoretical and that no model can guarantee the absence of decompression sickness (maker statement).
• DAN's medical reference says dive tables and computers are models that cannot capture every factor affecting gas exchange, so divers should not over-rely on them, and DAN's decompression illness page says decompression sickness can occur even when accepted guidelines have been followed.

We never say a computer is safe or certified. PADI says batteries should be handled as the maker instructs.

What the standard does and does not cover

The European standard for depth instruments is EN 13319:2000, "Diving accessories, Depth gauges and combined depth and time measuring devices, Functional and safety requirements, test methods". It covers depth gauges, the depth function of other instruments, and depth-and-time functions. Its scope expressly excludes any information other than depth and time, including any decompression information a device displays. So a computer that claims to meet EN 13319 is making a claim about its depth and time readings, not about its decompression calculations.

What a dive computer does

PADI says a computer combines depth and time data with a decompression model that estimates nitrogen uptake and shows remaining no-stop time, and that it can also replace a separate depth gauge, timer and sometimes the pressure gauge. Its 2026 blog says computers model gas uptake and release with theoretical tissue compartments (some use 16), account for previous dives, and replaced PADI's RDP table and The Wheel, and that each computer uses its own algorithm. The first recreational computers appeared in the 1980s, with air integration, ascent-rate indicators and nitrox modes added in the 1990s.

Our picks by category

Algorithms, as makers and one study describe them

Makers name the decompression model a computer runs. As Suunto describes its own models (maker statements):

• Buhlmann 16 GF: based on Swiss physician Dr Albert A. Buhlmann's ZHL-16C, a dissolved-gas model with 16 theoretical tissue groups, with conservatism set by gradient factors. Suunto flags non-default values as outside its recommendation.
• RGBM: Suunto says it adopted Dr Bruce Wienke's Reduced Gradient Bubble Model in the late 1990s, and describes its Fused RGBM 2 as a bubble model using 15 tissue groups (maker claim).

An independent study (Doug Fraedrich, Diving and Hyperbaric Medicine, 2018) tested four algorithms, ZHL-16C, VPM-B, Suunto-RGBM and the Cochran EMC-20H, against reference criteria. None of the four passed every test at factory-default settings. The study classes VPM-B and Suunto-RGBM as bubble models and ZHL-16C as a dissolved-gas model. Sources also disagree on deep stops, which bubble models such as VPM-B tend to add: a retailer's training blog notes that recent research questions their benefit, and the Fraedrich study found VPM-B's first stop always deeper than its reference. We name the disagreement; we do not settle it.

Rental computers

DAN's Alert Diver (2023) says divers using a rented computer should be able to read its key displays and alerts, and should check its gas setting and transmitter pairing, because some computers keep the previous user's settings. PADI's 2016 blog lists familiarity with how your own computer works among the benefits of owning gear.

Nitrox and flying

PADI lists nitrox compatibility as a standard feature; agencies train divers in nitrox use (see specialty certifications). PADI's blog (updated 2024) tells divers to follow their computer's no-fly time and recommends 24 hours before flying after any diving, while DAN's 2002 workshop consensus suggests at least 12 hours after a single no-decompression dive and 18 hours after multiple dives per day or multiple days. Those are each body's published figures, not rules; see flying after diving.

Care

PADI says to rinse a computer in fresh water after use, keep it out of direct sun, protect it from drops, store it cool and dry, and handle batteries as the maker instructs.