Dive tables vs dive computer — what's the difference?
Updated 2026-06-30 · Dive Planning
The difference is planning by hand versus tracking in real time. Dive tables are printed charts (like the Recreational Dive Planner) you use before the dive to look up your no-decompression limit for a planned depth and time. A dive computer is a wrist or console device that measures your actual depth and time throughout the dive and continuously recalculates your remaining no-stop time for you.
Today almost every diver uses a computer, but you'll still learn the principles behind tables in your Open Water course — because understanding how the limits work makes you a safer diver, computer or not.
How dive tables work
Tables assume you spend your whole dive at the deepest point (a 'square' profile), which makes them conservative but simple. You find your no-decompression limit from depth and time, track a 'pressure group' for residual nitrogen, and add surface-interval credit before a repetitive dive. They need no batteries and are a great backup.
How a dive computer works
A computer samples your real depth every few seconds and credits you for time spent shallower, so it allows longer, multilevel dives than a table would. It shows remaining no-stop time, ascent rate, safety-stop timing and your previous dives — all live. The trade-off: it's an electronic device, so you check the battery and never dive beyond what it shows.
Which should you use?
Use a dive computer as your primary tool — it's safer and gets you more bottom time — and understand tables as backup knowledge. Whichever you use, you follow the more conservative reading and add a safety stop. Both are built on the same decompression science; they just apply it differently.
Frequently asked questions
Do I still need to learn dive tables?+
Your entry-level course teaches the concepts so you understand no-decompression limits, pressure groups and surface intervals. In practice you'll dive with a computer, but the table knowledge is your backup and your foundation.
Is a dive computer safer than tables?+
For most diving, yes — it tracks your actual depth profile in real time instead of assuming a worst-case square profile, and it monitors ascent rate and safety stops live. You still dive conservatively and within its limits.
What happens if my dive computer fails underwater?+
End the dive following your training: ascend slowly, make a safety stop, and surface. That's exactly why divers learn the table principles and often dive with a backup computer or a planned profile.