Scuba Diving Air Consumption Calculator
Calculate how long your scuba tank will last at any depth.
Enter tank size, start pressure, SAC rate, and depth to get estimated dive time.
Tank duration tells you how long your scuba cylinder will last at a given depth before you must begin your ascent. Planning dive time is essential for safety — running out of air underwater is one of the most dangerous situations a diver can face.
Formula:
Duration (min) = (Usable gas volume) / (SAC rate × Absolute pressure)
Step-by-step breakdown:
-
Usable gas volume (liters) = (Start pressure − Reserve pressure) × Tank volume Example: (200 bar − 50 bar) × 12 L = 1,800 liters
-
Absolute pressure at depth = 1 + (Depth in meters / 10) At 20 m: 1 + 20/10 = 3 bar (absolute) At the surface: 1 bar (absolute)
-
Duration = Usable volume / (SAC × Absolute pressure) Example: 1,800 / (20 × 3) = 30 minutes
SAC rate (Surface Air Consumption): Your SAC rate is how many liters of air you breathe per minute at the surface. It varies by fitness, experience, and stress level.
- Beginner diver: 25–30 L/min
- Recreational diver: 15–20 L/min
- Experienced diver: 10–15 L/min
- Technical diver: 10–12 L/min
Common tank sizes:
| Tank | Volume | Working pressure | Capacity |
|---|---|---|---|
| Standard aluminum (80 cu ft) | 11.1 L | 207 bar | 2,300 L |
| Steel 12 L | 12 L | 200–230 bar | 2,400–2,760 L |
| Steel 15 L | 15 L | 200 bar | 3,000 L |
| Pony bottle | 3–6 L | 200 bar | 600–1,200 L |
Safety note: Always plan to surface with a minimum of 50 bar (500–600 liters) reserve. This gives you air for a safety stop at 5 meters (3 minutes minimum) and margin for emergencies. Never plan a dive that uses your entire tank — conditions change underwater.