Scuba SAC Rate Calculator

How it works

Gas used = (start − end) ÷ rated pressure × tank capacity · ATA = depth(ft) ÷ 33 + 1 · Depth rate = gas used ÷ time · SAC = depth rate ÷ ATA

Surface Air Consumption normalises how fast you breathe down to sea-level pressure, so it stays comparable across dives at any depth. Air is compressed as you descend — at 33 ft you are at 2 atmospheres and breathe twice the surface volume per breath — so dividing the at-depth consumption by the ambient pressure in ATA gives your true personal rate. Knowing your SAC lets you predict how long a given tank will last at any planned depth, which is the foundation of gas planning. Recreational divers typically fall between 0.5 and 0.8 cu ft/min.

Worked example

You breathe an aluminium 80 (77.4 cu ft at 3,000 psi) from 3,000 down to 1,000 psi — 2,000 psi, or 2000/3000 × 77.4 = 51.6 cu ft — over 30 minutes at 60 ft. Depth is 60/33 + 1 = 2.82 ATA, at-depth rate is 51.6/30 = 1.72 cu ft/min, so SAC = 1.72 ÷ 2.82 ≈ 0.61 cu ft/min.

Frequently asked questions