Depth, Air & Time
How Long Does a Scuba Tank Last?
Why the same tank lasts 90 minutes on one dive and 30 on another — and how to make your air go further.
A standard aluminium 80 (11 L) tank lasts roughly 45–60 minutes on a typical recreational dive — but the real answer depends on depth, tank size, your breathing rate (SAC), and how active or relaxed you are. Shallow and calm = much longer; deep and busy = much shorter.
- Common tank
- Aluminium 80 (11 L)
- Typical dive
- 45–60 min
- Shallow (10 m)
- Up to ~90 min
- Deep (30 m)
- ~30–40 min
What affects how long your air lasts
- Depth — the biggest factor. At 20 m you breathe air three times faster than at the surface, so depth dramatically shortens dive time.
- Tank size — bigger tanks hold more gas (see below).
- Your breathing rate (SAC) — how much gas you use per minute. Relaxed, experienced divers use far less.
- Activity & stress — fighting current or feeling anxious burns air quickly; calm, slow diving stretches it.
- Fitness & technique — good buoyancy and efficient finning save a surprising amount of gas.
Common tank sizes
| Tank | Capacity | Best for |
|---|---|---|
| Aluminium 80 (S80) | 11.1 L / 80 cu ft | The standard recreational tank |
| 10 L | ~77 cu ft | Smaller divers, lower air use |
| 12 L | ~92 cu ft | Longer dives, higher air use |
| 15 L | ~115 cu ft | Air-hungry or technical divers |
| Pony bottle | ~3 L | Backup / redundant air supply |
A rough way to estimate dive time
Air consumption multiplies with depth: at 10 m you use ~2× your surface rate, at 20 m ~3×, at 30 m ~4×. So a tank that would last ~3 hours at the surface gives only ~45 minutes at 20 m. Always surface with a reserve — ascend before you reach 50 bar / 500 psi.
Want a real number for your dive? Estimating gas by feel is unreliable. The Gas & SAC planner in the Diving Standard app calculates exactly how long your tank will last at a given depth using your personal breathing rate — and tells you your turnaround pressure.
Plan your air with the Gas & SAC planner
Stop guessing how long your tank will last. Diving Standard's Gas & SAC planner gives you a precise, personalised dive time — and free lessons to learn the theory behind it.
Get the Diving Standard appFrequently asked questions
How long does a scuba tank last at 18 metres?
For an average diver on an aluminium 80, roughly 45–55 minutes at 18 m. Deeper dives are shorter; shallower dives can exceed an hour.
Why does my buddy's air last longer than mine?
Mostly breathing rate (SAC). Relaxed, fit, well-trimmed divers with good buoyancy use far less gas. It improves quickly with experience and calm, slow breathing.
What pressure should I surface with?
Plan to begin your ascent before you reach 50 bar / 500 psi, leaving a safe reserve for your safety stop and any unexpected delays.