Dive Gas Consumption Calculator (SAC / RMV)
How much gas a dive at a given depth and time uses, the cylinder pressure left, and the longest bottom time that keeps your reserve.
Results
Gas used
2240
L
Pressure used
187
bar
Pressure left at the end
13
bar
Longest time at that depth keeping the reserve
32
min
Reserve kept?
No
What this tool does
Gas consumption scales with ambient pressure: at 10 m you breathe twice as much gas per minute as at the surface, at 30 m four times. Start from your own surface air consumption, measured on relaxed dives, and remember it rises with cold, current, stress and effort. This counts only the time at depth; the descent, ascent and safety stop use gas too, and gas is treated as ideal. Agree the reserve with your buddy and your training — 50 bar is a common minimum on recreational dives.
Formula
gas = SAC × (depth ÷ 10 + 1) × time · pressure used = gas ÷ cylinder volume
Variables
| Symbol | Meaning | Unit |
|---|---|---|
sac | Surface air consumption (SAC) | L/min |
d | Average depth | m |
tm | Time at that depth | min |
cv | Cylinder size (water volume) | L |
cp | Starting cylinder pressure | bar |
rs | Reserve to keep | bar |
G | Gas used | L |
PU | Pressure used | bar |
PL | Pressure left at the end | bar |
MT | Longest time at that depth keeping the reserve | min |
RK | Reserve kept? | — |
Worked example
- Surface air consumption (SAC)20 L/min
- Average depth18 m
- Time at that depth40 min
- Cylinder size (water volume)12 L
- Starting cylinder pressure200 bar
- Reserve to keep50 bar
- Gas used2240 L
- Pressure used187 bar
- Pressure left at the end13 bar
- Longest time at that depth keeping the reserve32 min
- Reserve kept?No
Limitations
- Planning figures only. Diving with enriched air or planning gas needs proper training and certification, a dive computer and an analysed cylinder; never rely on a web calculator in the water.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.