Surface Air Consumption (SAC) — What It Is and Why It Matters
Surface air consumption (SAC) rate is a standardized measure of a diver's gas consumption expressed as the volume of gas used per minute at the surface (1 ATA). It normalizes consumption across different depths, making it useful for gas planning. SAC is calculated by dividing the total gas used (in bar or PSI, converted to liters) by the dive time and the average ambient pressure.
A typical recreational diver has a SAC rate of 14 to 20 liters per minute. Technical divers use SAC rates extensively for gas planning — calculating how much bottom gas, decompression gas, and bailout gas they need for a given dive plan. Tracking your SAC rate over time helps you monitor improvements in efficiency.
Frequently Asked Questions
How do I calculate my SAC rate?
Record your starting and ending tank pressure, dive time, and average depth. Calculate gas used in liters, divide by dive time in minutes, then divide by average ambient pressure in ATA. For example: used 1200 liters in 40 minutes at an average of 15 meters (2.5 ATA) = 1200 / 40 / 2.5 = 12 liters per minute SAC.
Do dive computers show SAC rate?
Many air-integrated dive computers calculate and display SAC rate automatically in their dive log summaries. Real-time SAC display is less common but available on some models. Companion apps often provide SAC rate analysis across your dive history.
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