Scuba Tank Duration Calculator
Calculate how long a scuba tank will last at a given depth.
Enter tank size, pressure, and your surface air consumption (SAC) rate.
A scuba tank lasts less time the deeper you dive because you breathe compressed air at ambient pressure. At 10 m (33 ft), pressure is 2 ATA — you use air twice as fast as at the surface.
Formula: Duration (min) = (Tank volume × Pressure) / (SAC × (depth/10 + 1))
Where: Tank volume is in liters (or use cubic feet for imperial), pressure in bar, SAC is Surface Air Consumption rate in L/min, and depth/10 + 1 gives absolute pressure in atmospheres.
Converting to cubic feet (imperial): Duration (min) = (Tank pressure in PSI × Tank volume in cu ft) / (SAC in cu ft/min × (depth/33 + 1))
Typical SAC rates:
- Beginner diver: 20–25 L/min
- Recreational diver: 15–20 L/min
- Experienced diver: 12–16 L/min
- Instructor/cave diver: 10–13 L/min
Common tank sizes: AL80 aluminum tank: 11.1 L / 80 cu ft at 200 bar (3000 PSI). Steel 100: 14 L / 100 cu ft. Pony bottle: 3–5 L.
Safety rule: Never surface with less than 50 bar (700 PSI). Always plan for a 3-minute safety stop at 5 m (15 ft) at the end of the dive. The rule of thirds: use ⅓ going out, ⅓ returning, keep ⅓ in reserve.