Two divers enter the water with identical cylinders. Forty minutes later one is signalling the group up while the other still has half their gas. The difference is almost never lung size or fitness — it is breathing pattern, trim, weighting and how relaxed each of them is. All four are learnable, and improvements of a third or more over a season are common rather than exceptional. Here is what actually drives air consumption, the breathing technique that works, the one technique that is dangerous, and how to measure whether you are getting better.
Why Air Disappears Faster Underwater
The first reason is physics and you cannot argue with it. Every ten metres of depth adds roughly one bar of ambient pressure, and your regulator delivers air at ambient pressure. At 20 metres you are breathing at three bar absolute, so each identical breath contains three times as many molecules as the same breath at the surface. A cylinder that lasts an hour at 10 metres lasts around 40 minutes at 20.
Everything else is under your control. Exertion is the largest single factor — swimming twice as fast costs roughly four times the energy, because drag rises with the square of speed. Cold raises consumption because the body burns energy maintaining core temperature, and it does so long before you consciously feel cold. Stress produces fast, shallow breathing that moves the same air in and out of the upper lungs without properly exchanging it, which is both inefficient and self-reinforcing. And poor configuration — excess lead, head-up trim, dangling gear — creates continuous low-level work you are not aware of doing.
Regulator breathing resistance is real but minor on a modern, well-serviced set. If your regulator is genuinely hard work to breathe from, that is a servicing problem rather than a technique problem.
The Breathing Pattern That Works
On land most people breathe shallowly into the upper chest without thinking about it. Underwater that pattern is inefficient, because the air that stays in the airways and upper lungs never reaches the alveoli where gas exchange happens — you use the gas without getting the benefit of it.
Breathe with the diaphragm. On the inhale the abdomen should expand first and the chest afterwards; on the exhale the abdomen draws back in. It moves considerably more air for less muscular effort and naturally slows the whole cycle down. Practise it on land with a hand on your stomach until it is the default, because you will not learn a new breathing pattern for the first time at 15 metres.
Make the exhale longer than the inhale. A rhythm of roughly four counts in, a brief natural pause, six to eight counts out, then another short pause. The long exhale is the important half: it clears carbon dioxide properly, and it is rising carbon dioxide rather than falling oxygen that creates the urge to breathe faster. Divers who feel breathless underwater are usually under-exhaling, not under-inhaling.
Keep it smooth and continuous. No gulping, no forcing, and never a held breath. The pauses at the top and bottom of the cycle are relaxed moments, not breath-holds — the difference matters both for safety and for how the pattern feels after twenty minutes.
Why Skip-Breathing Is a Bad Idea
Skip-breathing means deliberately holding a long pause after each inhale to stretch a cylinder, and it circulates as a tip among divers who should know better. It does not work and it is genuinely risky.
Holding air in the lungs does not reduce how much you consume; it reduces how often you exchange it, so carbon dioxide accumulates. The consequences are headaches after the dive, impaired judgement during it, reduced tolerance to narcosis and, in the worst case, a rapid onset of air hunger that ends in panicked breathing — at which point you consume far more gas than you saved. Any breath-holding also carries lung-overexpansion risk if your depth changes while the airway is closed, which is the one mechanism in recreational diving that injures people quickly.
The pattern above achieves the same goal safely: a long, complete exhale genuinely lowers consumption, whereas a held inhale only postpones it.
What Matters More Than Breathing Technique
Correct weighting
Overweighting forces you to carry air in the BCD, which expands and contracts with depth and demands constant correction. It is the single largest avoidable drain on gas. Redo a proper buoyancy check — see weights and belts.
Flat trim
Head-up, feet-down means every kick drives you upward, which you correct by venting, which makes you sink. Lying horizontal removes that loop entirely and roughly halves your drag. Usually fixed by moving lead higher, not by trying harder.
Slowing down
Drag rises with the square of speed, so swimming twice as fast costs about four times the energy. The most efficient divers look almost lazy. Long, slow kicks from the hip beat fast kicks from the knee on every measure.
Staying warm
A cold diver burns energy on thermoregulation well before they notice being cold. A hood is usually the cheapest improvement available, and an adequate suit pays for itself in bottom time.
Being relaxed
Nervousness produces fast shallow breathing, and fast shallow breathing produces the sensation of not getting enough air, which produces more nervousness. Diving within your limits and rehearsing emergency skills until they are dull is what breaks the loop.
Streamlining
Dangling hoses, gauges and cameras add drag all dive and snag on everything. Clipping them off is free and noticeable. See clips and retractors.
Measuring Whether You Are Actually Improving
Comparing “bar used” between dives tells you almost nothing, because depth and duration differ every time. What you want is consumption normalised to the surface, and there are two common ways to express it.
SAC in bar per minute is the quick version. Take the pressure you used, divide by the dive time in minutes to get bar per minute at depth, then divide by the absolute pressure at your average depth — average depth divided by ten, plus one. A dive averaging 20 metres where you used 120 bar in 40 minutes gives 3 bar/min at depth, divided by 3 bar absolute, so a SAC of 1 bar/min at the surface.
The catch is that this number is tied to your cylinder size: the same breathing in a 10-litre cylinder and a 15-litre one produces different figures. That is fine for tracking your own progress with the same tank, and useless for comparing yourself with anyone else.
RMV in litres per minute fixes that. Multiply your SAC by the cylinder’s volume in litres — 1 bar/min in a 12-litre cylinder is 12 litres per minute. This is the number that is comparable between divers and across equipment. Typical recreational figures sit somewhere in the teens to low twenties, and improving from the low twenties to the mid teens over a season is an entirely realistic outcome.
Record it in your logbook along with the conditions: suit, cylinder, average depth, water temperature and whether there was current. One number in isolation means little; the trend across twenty dives is what tells you whether the work is paying off.
Training That Helps
- Diaphragmatic breathing on land: Ten minutes a day, hand on the abdomen, four counts in and six to eight out. The point is to make the pattern automatic before you need it underwater.
- General aerobic fitness: Swimming, running or cycling. It raises the exertion level at which your breathing becomes laboured, which is the whole mechanism.
- Core work: A stable core is what lets you hold horizontal trim without constant small corrections.
- Leg strength and kick technique: Efficient kicks from the hip, not the knee. Practising frog kick alone will change your consumption more than any breathing exercise.
- Hovering drills: Set neutral buoyancy in a pool or shallow water and hold position using breathing alone. This is the single most transferable in-water exercise there is.
- A pre-dive routine: Five minutes of slow, deliberate breathing before you enter the water. Starting calm is easier than becoming calm at depth.
- Dive frequently: Skills and comfort decay faster than people expect. Regular short dives beat occasional long trips.
- One thing per dive: Pick a single focus — trim, kick, or breathing rhythm — and review it afterwards rather than trying to fix everything at once.
One thing deliberately not on that list: breath-hold swimming in a pool. Repeated hypoxic training in water carries a real risk of blackout without warning, and it has killed competent swimmers. Whatever marginal benefit it might offer for diving is not worth that, and none of the improvements above depend on it.
What You Cannot Change
Some of the variation between divers is fixed. A larger person has a larger lung volume and a higher metabolic rate and will use more gas than a smaller one doing exactly the same dive — this is arithmetic, not a skill gap, and comparing absolute consumption between differently sized divers is meaningless. Lung capacity declines gradually with age, and individual efficiency of oxygen use varies genetically.
None of that limits how much you can improve relative to yourself, which is the only comparison that matters. The honest framing is that a large diver with excellent technique will still use more gas than a small diver with excellent technique, and both will use dramatically less than they did before they worked on it.
The Equipment Side
A regulator that breathes hard makes every one of the techniques above harder to apply, and divers often attribute to themselves what is actually a servicing issue. If inhalation feels like work, if you notice a delay before gas arrives, or if the set breathes noticeably differently at depth than at the surface, it needs attention. Service annually regardless of how it feels, because seats and o-rings degrade on a calendar. Check that the second stage’s adjustment, if it has one, is not left wound down from a previous dive. See regulators.
Suit fit matters more than suit thickness. A loose suit flushes cold water continuously, and a cold diver breathes more regardless of technique; a suit that is too tight restricts chest expansion and prevents the deep diaphragmatic breathing this entire article rests on. If you cannot take a full comfortable breath in your suit on land, you will not manage it at depth.
Fins and weighting are the other two levers. Blades stiffer than your legs can drive produce cramp and hard breathing rather than speed, so if you finish dives with sore calves, go softer — see fins with strap. And redo your buoyancy check properly whenever you change suit, cylinder or water type; most divers are carrying lead they no longer need from a figure set during their first course.
Our guides to the skills that make a good diver and choosing equipment cover both of these in more depth.
FAQ
What is a good air consumption rate?
Expressed as RMV — litres per minute at the surface — typical recreational figures run from the mid teens to the low twenties, and experienced divers often sit lower. Body size alone shifts that range substantially, so the useful comparison is against your own previous dives, not against a buddy. Track the trend across twenty dives rather than reading anything into a single number.
Should I breathe slowly to use less air?
Slowly and deeply, yes; less often through breath-holding, no. A long complete exhale genuinely lowers consumption because it clears carbon dioxide properly and lets the next breath do real work. Holding an inhale — skip-breathing — only postpones consumption while accumulating carbon dioxide, which causes headaches, impairs judgement and risks ending in panicked breathing that costs far more gas than it saved.
Why does my buddy use so much less air than me?
Usually some combination of body size, weighting, trim and speed rather than lung discipline. Larger divers use more gas doing an identical dive, which is physiology and not a fault. Beyond that, check whether you are overweighted, whether you swim horizontally, and whether you are moving faster than they are. Those three explain most of the gap between divers of similar size.
Does diving nitrox reduce air consumption?
No. You breathe exactly the same volume of gas regardless of its oxygen content, so a cylinder of nitrox lasts no longer than a cylinder of air. What nitrox extends is your no-decompression limit, because there is less nitrogen in each breath. On shallower dives where gas rather than nitrogen is your limiting factor, nitrox changes nothing at all.
How do I calculate my SAC rate?
Take the bar you used, divide by dive time in minutes to get bar per minute at depth, then divide by the absolute pressure at your average depth — that is average depth divided by ten, plus one. To convert it into a figure comparable between divers, multiply by your cylinder’s volume in litres to get RMV. Record it with the conditions, since cold, current and depth all move it.
Will getting fitter improve my air consumption?
Yes, though indirectly. Aerobic fitness raises the level of exertion at which your breathing becomes laboured, so the same swim costs you less. Core strength helps you hold trim without constant correction, and leg strength makes kicks more efficient. But technique, weighting and staying relaxed produce larger gains faster than fitness alone, and a relaxed unfit diver routinely outlasts a tense athletic one.
Is breath-hold training in a pool useful for scuba divers?
It is not worth the risk. Repeated breath-holding in water can cause blackout with no warning signs beforehand, and it has killed strong swimmers doing exactly this. None of the improvements that matter for scuba depend on it — diaphragmatic breathing practice, aerobic fitness, hovering drills and better trim deliver more, safely. If you want to train breath-holding, do it dry and never alone in water.
Why do I get a headache after diving?
Carbon dioxide retention is a common cause, and it usually comes from shallow breathing, skip-breathing, or working hard against a current or a stiff regulator. Other frequent causes are dehydration, a mask strap or hood worn too tight, and jaw tension from gripping the mouthpiece. If headaches are regular, look first at your breathing pattern and at whether your regulator needs servicing.