How fast the published guidance says to come up, for the kind of dive you are doing — with the depth bands from the swimming pool to the Challenger Deep, and what a submersible does differently.
ascent —
Reference only — this is not a dive plan
Decompression sickness can paralyse or kill, and it can happen on dives that followed every rule.
This page summarises published ascent-rate guidance so you can see how the numbers compare. It is not training,
not a dive table and not a dive computer, and it cannot know your gas, your body, your equipment, the water or the
day.
Get a dive licence. Learn to dive with a recognised training agency, and hold the certification for the depth and the kind of diving you are doing.
Speak to qualified professionals — an instructor, a dive centre, or a diving doctor (hyperbaric medicine) — about anything you are unsure of. Do not use a web page to decide.
Dive with a buddy or a professional, follow the plan you were trained to make, and let your own dive computer and training set your ascent.
If you have symptoms after a dive (unusual pain, numbness, tingling, rash, breathlessness, dizziness, extreme tiredness): breathe 100% oxygen if you have it, call the emergency services, and contact a diving emergency service such as DAN. Do not go back down to treat yourself.
Your dive
—
Metric first, feet shown beside it. Pressure uses the diver’s convention of 10 m of seawater to one bar.
Diving above sea level?
Above about 300 m (1,000 ft) of elevation the air above the water is thinner, and the depth you must plan for is deeper than the gauge says. The Altitude & Depth tool works out the correction for your lake: open Altitude & Depth.
How fast is too fast
m/min
—your ascent rate
The ascent, drawn
—
Where the depth bands sit
human to submersible
The colours are how much guidance and training the depth calls for, not a promise of safety at any depth: green for the range taught to beginners, amber where narcosis and oxygen toxicity start to bite, orange for technical diving with mandatory decompression, red for the extreme end, purple for the records that need a chamber or a one-atmosphere suit, and blue where only a pressure hull goes.
Every way of coming up, on one scale
metres a minute, log scale
A diver breathing gas at depth has to come up slowly, because the gas dissolved in the body comes out as the pressure falls. A crew in a submersible, a one-atmosphere suit or a breath-hold diver are in different situations, which is why the rate that is dangerous for one is simply how the other travels.
Where these numbers come fromAscent rates are those published by the US Navy and NOAA (30 ft/min), the Bühlmann tables (10 m/min), BSAC 88 and MN90 (15 m/min) and the dive-computer makers, as summarised by DAN and the decompression literature; depth records are from Guinness World Records and the vehicles’ operators; the flying-after-diving figures are DAN’s. The 15 m/min and the depth-varying computer range are the least well sourced. Nothing here calculates a dive limit or a decompression schedule, and none of it replaces training, a dive computer or a doctor. Get a dive licence and dive with qualified professionals.
Levels of guidance
What each source says, and what kind of source it is
There is no single number. A standard is a rule written into a navy or national diving manual; a table carries a rate with its mathematics; a training agency sets a limit and recommends something gentler; a dive computer applies its own maker’s model, and many penalise a fast ascent with extra stop time. The rows are ordered from the gentlest to the fastest.
Rates are as published in the manuals and summaries cited on the Sources page and may have changed: read the current edition of your own agency, table or computer manual. Feet per minute in brackets.
People and pressure hulls
Why a submersible does not get the bends
A diver breathes gas at the pressure of the water around them, so every extra 10 m puts more gas into the blood and tissues, and the way back up has to give it time to leave. A crewed submersible, and an atmospheric diving suit, keep one atmosphere inside a hull that carries the pressure instead: nothing dissolves, so there is no decompression, and the ascent rate is set by ballast and the vehicle rather than the occupants’ bodies.
After the dive
Flying after diving
A pressurised aeroplane cabin is at about the pressure of 2,000–8,000 ft (roughly 600–2,400 m), which is a drop in pressure like a small ascent, so nitrogen still in the body can form bubbles. DAN’s guidance, for divers without symptoms:
One no-stop dive
at least 12 hours on air or nitrox, before flying.
Several dives, or several days
at least 18 hours
Dives with decompression stops
well over 18 hours there is little data, so DAN says “substantially longer than 18 hours appears prudent”.
The simple rule
24 hours DAN suggests allowing a minimum of 24 hours to cover fatigue, dehydration and cabin emergencies.
Your dive computer, training agency and doctor may give a different or longer figure. Drive over a mountain pass is the same problem: check the elevation of the road in Altitude & Depth.
The honest part
What this page is not
It does not calculate a no-stop limit, a decompression schedule, a gas plan or a surface interval, and it will not. Those depend on the model your computer or table uses, your gas, your workload, the temperature, your fitness and the dives you did yesterday; a rounded figure from a web page would be a hazard, not a help. It shows how the ascent-rate guidance compares, so that when your instructor gives you a number you can see where it sits.
Is 18 m a minute safe?
It is the older maximum in some training-agency tables, but it is not the gentlest current guidance. DAN notes that the US Navy moved from 60 to 30 feet a minute after studies found slower ascents caused fewer cases of decompression sickness, and that a 2009 study found a 60 ft/min ascent produced higher bubble grades than 30 ft/min. Bubbles are not the same as decompression sickness, but they are what the guidance is trying to reduce. A slower ascent is almost always the better choice.
Why 9 and 10, and not one number?
30 feet a minute, the US Navy and NOAA figure, is 9.1 metres a minute. Many tables and computers round to 10 metres a minute. They are the same guidance in different units and the difference is small compared with the difference between 10 and 18.
What is the safety stop for?
It is a pause, typically one to five minutes at three to six metres, that gives the gas in the tissues longer where the pressure changes fastest. Many agencies and computers recommend one on any dive beyond a certain depth and time, and a computer may make it mandatory after a fast ascent. It is a margin: it does not turn a dive that needed mandatory decompression into one that did not.
Can I come up too slowly?
On a short dive barely. On a dive near a no-stop limit or with decompression stops, time spent ascending is time still absorbing gas in the deeper tissues, so a plan or computer counts a slow ascent as part of the dive. Follow your plan rather than inventing a slower rate.
Do freedivers get decompression sickness?
They can. Breath-hold divers carry only the gas in one breath, so a single dive is safe from it, but repeated deep dives with short rests can build it up (called taravana). Their larger risk is a blackout in the last ten metres of the way up. Common guidance is to rest at least twice the dive time between deep dives; learn from a qualified freediving instructor.
What does this page assume?
Seawater at 10 m to one bar, which is the conventional rounding (the physical figure is about 9.95 m); sea level; a healthy, rested, hydrated diver on a single dive. The ascent figures are those published in the sources listed on the Sources page and are guidance for ordinary recreational diving, not limits that guarantee safety. The oxygen limits are the common 1.4 and 1.6 bar working and contingency values. Verified in dive_model.py.
Field notes
Reading the water
2 → 1 bar
The last ten metres do the most
Going from 10 m to the surface halves the pressure; going from 40 m to 30 m is 5 bar to 4, a change of a quarter. The same ten metres is a far bigger step in the shallows, which is why some computers allow a faster ascent at depth and a slower one near the top, and why the safety stop sits where it does.
Slow is a plan, not a habit
Slowing right down is not automatically safer. On a dive near its limit, or with decompression, the time spent ascending is time still taking gas into the slower tissues, so a plan counts a slow ascent as part of the dive. Follow the ascent your plan or computer expects.
A safety stop is a margin
A pause of a few minutes at three to six metres gives the gas more time to leave where the pressure falls fastest, and most agencies recommend it on deeper dives. It is not a licence to push the dive further, and it does not replace a mandatory decompression stop.
Smaller than your smallest bubbles
A rule taught on courses is never to swim up faster than your smallest bubbles. It is a rough check without a computer, but a computer or gauge that shows ascent rate directly is better, and an inflating buoyancy device can carry you up faster than you feel.
332 m / 10,935 m
Two different kinds of record
The deepest scuba dive, 332 m, took a team of support divers and hours of decompression. The deepest crewed dive went more than thirty times deeper in a hull holding one atmosphere. Records for people and for vehicles answer different questions.
Version history · site-wide passes only
This page has changed in 56 archived releases, but each of those was a site-wide pass, so none is attributable to this tool on its own and none is listed here. That is not a claim that the tool never changed — a release that reworked many pages at once may well have altered this one too. The changelog has them.
Not for dive planning. This page is a reference for how published ascent-rate guidance compares. It is not a dive table, a computer, a decompression calculator or training. Get a dive licence, dive with qualified professionals, and speak to a dive instructor or a diving doctor about anything you are unsure of. No responsibility is accepted for any use of it in diving.
Rules of thumb are approximations, offered to get you to the right order of magnitude fast. Check anything load-bearing against its source or the exact tool. Privacy·Terms