Scuba Air Consumption Calculator

Your Surface Air Consumption (SAC) rate is the standard yardstick divers use to compare breathing efficiency independent of tank size or depth: it expresses how many liters of air you burn per minute at surface pressure (1 atmosphere). This calculator first converts your logged pressure drop into total air consumed — tank volume times the difference between start and end pressure — then divides by dive duration and by ambient pressure at your average depth (1 + depth/10, since pressure increases roughly 1 atmosphere per 10 meters of seawater) to normalize the number back to the surface. The reported "Consumption at Depth" reverses that normalization, multiplying SAC by the same ambient-pressure factor, showing how much air you actually burn at the depth you dived.

From there, the calculator estimates how many more minutes you could stay at that same depth: it takes the air still in the tank at your ending pressure, subtracts a fixed 50-bar reserve that should never be breathed into on a working dive, and divides the remainder by your at-depth consumption rate. The rate rating buckets your SAC into four bands — under 12 L/min is excellent, 12 to 17 average, 17 to 22 high, and above 22 very high — useful for tracking whether experience and better trim are improving your air efficiency over time. Because SAC assumes a roughly constant breathing rate across the whole dive, a single deep or strenuous segment can distort the average; use several dives at similar profiles for a more reliable baseline, and never treat the bottom-time estimate as a substitute for watching your gauge.