Air Consumption Calculator — SAC Rate

⚠️ Warning — This tool is for informational purposes only and does not replace proper dive training or a dive computer. Your actual consumption varies with effort, stress, temperature and fitness. Always maintain sufficient safety reserve (minimum 50 bars). Formula based on Boyle's law.

Dive parameters

Tank volume (L)

Start pressure (bar)

End pressure (bar)

Depth (m)

Duration (min)

Reserve (bar)

SAC Rate

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Air Used

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Remaining Autonomy

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Assessment

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Understanding air consumption

SAC (Surface Air Consumption) is your air consumption rate normalized to surface pressure, expressed in litres per minute. It's an essential personal metric for dive planning.

Formula

SAC = (P_start - P_end) × Tank_volume / (Duration × Absolute_pressure)

Absolute pressure = 1 + depth/10. At 20m, you breathe 3 times more air than at surface (Boyle's Law).

Reference values

<15 L/min — Excellent. Experienced diver, calm efficient breathing
15-20 L/min — Normal. Most regular divers
20-25 L/min — High. Beginner, physical effort, or stress
>25 L/min — Very high. Intense work, strong current, or panic

FAQ

Why does my consumption vary between dives?

Consumption depends on many factors: physical effort (current, finning), stress, water temperature (cold increases consumption), wetsuit thickness, fitness level, and depth. Two identical dives can produce different SAC rates.

What safety reserve should I keep?

Standard rule: surface with minimum 50 bars reserve. For deep/technical dives, some use the rule of thirds (1/3 out, 1/3 back, 1/3 reserve). Never go below your reserve threshold.

Is a 12L tank enough for my dives?

For most recreational dives (<40m, <45min), a 12L at 200 bars works if your SAC is normal (<20 L/min). For deeper/longer dives or high consumption, consider a 15L or twin set.