The scuba air consumption calculator estimates dive bottom time from your tank size, SAC rate, and planned depth. Proper dive planning ensures you surface with adequate reserve air — the foundation of safe recreational diving.
Plan Your Dive Air
Average: 0.5-0.7 cu ft/min. Beginners: 0.8-1.0
Understanding Scuba Air Consumption
Air consumption in scuba diving is not fixed — it doubles with every additional atmosphere of pressure (every 33 feet of depth). At 33 feet, you breathe through twice as much air as at the surface. At 66 feet, three times as much. This is why bottom time decreases significantly at greater depths.
How to Measure Your SAC Rate
Track your air usage on known dives: record starting PSI, ending PSI, average depth, and bottom time. SAC = (Start PSI - End PSI) × Tank Volume / (ATA × Time). New divers typically have SAC rates of 0.8-1.2 cu ft/min. Experienced relaxed divers achieve 0.4-0.6 cu ft/min. Improving your SAC rate through buoyancy training and calm breathing is one of the most important skills in diving.
Rule of Thirds
The rule of thirds is standard in cave and technical diving and useful in all diving: use one third of your starting air for the first half of the dive, one third for the second half, and keep one third in reserve. This ensures you always have enough air to return from your farthest point, plus safety margin.
FAQ
Is this scuba air consumption calculator free?
Yes, completely free with no signup required.
What is SAC rate in scuba diving?
SAC (Surface Air Consumption) rate is the amount of air in PSI per minute you consume at the surface. Average divers consume about 0.5-0.7 cubic feet per minute at surface (or about 15-18 PSI/min in a standard 80 cu ft tank). Your SAC rate increases at depth — at 33 feet (2 ATA), consumption doubles; at 66 feet (3 ATA), it triples.
How do I calculate my SAC rate?
On a known dive: SAC = (Starting PSI - Ending PSI) × Tank Volume / (Depth in ATM × Dive Time in minutes). If you used 1,000 PSI over 30 minutes at 33 feet (2 ATM) on a standard AL80: SAC = 1000 × 0.077 / (2 × 30) = 1.28 cu ft/min.
What is the rule of thirds for air?
The rule of thirds states: use one third of your air for the descent and first part of the dive, one third for the return, and keep one third in reserve for emergencies. This is most critical for cave and overhead environment diving, but is a useful guideline for any dive.
What PSI should I surface with?
Most recreational dive training recommends surfacing with at least 500 PSI (34 bar) as a safety reserve. Many dive operators require 700 PSI minimum. Never descend or stay down if your air would drop below this level — surface before reaching it.