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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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