Dive Decompression Time

PADI Decompression Stops Calculator

Recreational dive computers and tables (PADI RDP, NAUI, SSI) estimate the No-Decompression Limit (NDL) at each depth. Go past that limit and your ascent has to include mandatory decompression stops, which give the inert gases (nitrogen, helium) time to off-gas safely. The standard safety stop sits at 5 m for 3 min. Once the NDL is exceeded, though, you pick up extra stops at deeper levels, and the exact pattern depends on whichever algorithm you're running.

The algorithms you'll meet most often are Bühlmann ZH-L16, a conservative compartment-based model; RGBM (Reduced Gradient Bubble Model), which Suunto uses; and VPM-B (Varying Permeability Model), a favourite in technical diving. They each handle tissue saturation and desaturation in their own way. When you plan multi-level or repetitive dives, cross-check the computer against a redundant table, and dial in a conservatism factor (GF Low/High) for cold water or hard-working profiles.

Applications

Recreational divers reach for it when planning dives past the NDL, technical divers use it on mixed-gas (Trimix) profiles, instructors lean on it to check student plans, and Brazilian Navy DHN (Diretoria de Hidrografia e Navegação) divers apply it under military protocols. The Caribbean, with its warm water and gentle current, is a world apart from cold-water sites like the Atlantic coast off Cabo Frio, and in cold water you should always crank up the conservatism.

FAQ

What is decompression sickness (DCS)? It happens when dissolved inert gases come out of solution and form bubbles as you ascend. Type I hits the muscles, joints and skin (the "bends"). Type II is neurological or pulmonary, a medical emergency that needs a hyperbaric chamber.

Is a safety stop the same as a decompression stop? No. A safety stop (3 min @ 5 m) is recommended but you can skip it. A decompression stop becomes mandatory once you've exceeded the NDL, and skipping that one drives your DCS risk way up.

What if I skip a required stop? Surface right away, breathe 100% oxygen if you have it, watch for DCS symptoms over the next 24–48h, and get in touch with DAN (Divers Alert Network) or the closest hyperbaric facility. Don't go back in the water to "decompress in-water" unless you have trained support on hand.