Tools you might need next
Calculate surface air consumption (SAC) rate for scuba divers. Enter tank PSI used, dive time, and depth to estimate cu ft/min at the surface.
Calculate enriched air nitrox MOD, EAD, and partial pressure of oxygen (ppO2) for scuba diving. Plan safe oxygen exposure limits at depth.
Plan decompression stops for technical scuba diving. Estimate required stop depths and times based on bottom time, depth, and gas mix for safe ascent.
At sea level, each 33 feet of seawater adds one atmosphere of pressure. Absolute pressure determines how quickly you consume gas compared to the surface.
P_abs = 1 + (Depth ft ÷ 33)Multiply surface air consumption by absolute pressure to find actual breathing rate at the planned average depth.
Rate at depth = SAC × P_abs (cu ft/min)Subtract reserve pressure (typically 500 PSI) from starting pressure, convert to cubic feet, and divide by consumption rate at depth. Apply a safety margin for ascent and unexpected delays.
Bottom time = Usable air (cu ft) ÷ (Rate at depth × safety factor)Updated: July 2026
With 3000 PSI start, 500 PSI reserve, SAC of 0.9 cu ft/min at 60 ft, plan roughly 25–30 minutes bottom time before reaching turn pressure.
Lower absolute pressure at 30 ft extends bottom time significantly. A diver with moderate SAC can enjoy 45+ minutes while maintaining the rule of thirds.
Plan using the higher SAC rate between buddies so the team surfaces together with adequate reserve. The calculator helps identify the limiting diver before entering the water.
Plan recreational no-decompression dives by matching your air supply to intended depth and personal consumption rate. Enter tank size, starting pressure, SAC rate, and target depth to estimate maximum bottom time, recommended turn pressure, and gas remaining at the surface.