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Your SAC Rate, Why It’s Important, and Why You Need To Know How To Calculate It!

By Jose Cernuda

One of the main things that separate experienced and efficient divers from novices is the amount of gas they consume during a dive. Efficient divers will use less gas than someone new and still learning to SCUBA dive. It’s not uncommon as a beginning diver to come back to the boat with just your reserve pressure while your instructor still has their tank half full.  So, how can you measure the amount of gas being consumed by a diver? This is where your SAC rate comes in.

What is SAC Rate?

Surface Air Consumption (SAC) rate is a measurement used to express how much gas a diver uses while diving. In the imperial system, it is measured in pounds per square inch (PSI) per minute. In the metric system, we measure surface air consumption in BAR per minute. It’s extremely important to understand that the measurement is expressed at the surface. Because atmospheric pressure increases as we dive deeper, the deeper we go, the more gas we consume.

This means that a diver who, for example, breathes 30 PSI per minute on the surface will use 60 PSI at 33 feet (10 meters) and 90 PSI at 66 feet (20 meters). As you can see from the image below, the deeper you go the more gas you will consume.