What is a no-decompression limit (NDL)?
Updated 2026-06-30 · Dive Planning
A no-decompression limit (NDL) is the longest time you can spend at a particular depth and still swim straight up to the surface — pausing only for a recommended safety stop — without having to make mandatory decompression stops along the way. It exists because your body absorbs nitrogen from the air you breathe under pressure, and that nitrogen needs to come out slowly.
The single most important thing to know: the NDL gets shorter the deeper you go, and your dive computer or dive tables track it for you in real time. Recreational diving is built around staying comfortably inside this limit.
Why the limit exists
Under pressure, your tissues absorb extra nitrogen (this is called 'on-gassing'). When you ascend, that nitrogen comes back out of solution. Ascend slowly and within limits, and it leaves harmlessly through your lungs. Stay too long or come up too fast, and it can form bubbles in your tissues and blood — decompression sickness ('the bends').
The NDL is simply the time budget that keeps your nitrogen load low enough to ascend directly and safely.
Deeper means less time
Because pressure (and therefore nitrogen uptake) increases with depth, no-stop times shrink quickly as you descend. Illustrative figures: you might have roughly an hour of no-stop time at 18 m / 60 ft, but only around 20 minutes near 30 m / 100 ft. Exact numbers vary by agency and table, so always follow your own computer or table — never a number from a website.
How divers stay safe
Your dive computer continuously tracks depth, time and nitrogen loading and shows your remaining no-stop time. Divers also plan conservatively, add a 3-minute safety stop at 5 m / 15 ft, ascend slowly, and pad in extra margin for cold, exertion or repetitive dives. On repeated dives, leftover ('residual') nitrogen reduces the NDL, which is why a good surface interval matters.
Frequently asked questions
What happens if you exceed the NDL?+
You incur a mandatory decompression obligation — meaning you must make staged stops on the way up to off-gas nitrogen safely. Exceeding the limit and ascending directly anyway risks decompression sickness. Recreational training teaches you to stay well within the NDL.
Does the NDL change with depth?+
Yes. The deeper you go, the faster you absorb nitrogen, so the no-decompression limit gets shorter. It's longest in shallow water and very short at recreational depth limits.
Who decides my NDL — the computer or the table?+
Whichever you're using is your authority for that dive, and you follow the more conservative one. Modern divers mostly rely on a dive computer, which calculates your remaining no-stop time live based on your actual depth profile.