Free scuba calculator
Surface Air Consumption Calculator
Calculate your Surface Air Consumption from a real dive using cylinder pressure, tank volume, gas mix, water temperature, average depth and dive time.
Real-gas correction
Air & Nitrox
Live calculation
Air consumption
Know what you really breathe.
Enter the values from your dive. The calculator shows both an ideal-gas estimate and a real-gas corrected result, then normalises the consumed gas to surface pressure to calculate your SAC.
bar
60 bar
050100150 bar
L
21% · AIR
21%28%32%36%40%
20 °C
10 °C15202530 °C
m
min
1. Gas used
The pressure drop is converted into litres of breathing gas. The real-gas estimate accounts for the fact that compressed gas does not behave perfectly ideally.
2. Pressure at depth
Average depth is converted to average ambient pressure using approximately 1 additional atmosphere every 10 metres.
3. Surface normalisation
Consumed gas is divided by dive time and average ambient pressure to give a surface-equivalent consumption rate.
Planning reference only.
SAC varies with workload, current, temperature, stress, equipment and other conditions. Use your own conservative planning values and follow your training and applicable diving standards.
FAQ
Surface Air Consumption, explained.
There is no single number that is good for every diver or every dive. The useful comparison is your own SAC across similar conditions and how much margin it gives you for conservative gas planning.
At cylinder pressures, breathing gas is not perfectly ideal. Its compressibility changes with pressure, temperature and composition, so a real-gas model can produce a different amount of surface-equivalent gas from the simple pressure × volume estimate.
The calculation uses the cylinder internal volume and pressure. Steel or aluminium can affect buoyancy and how a cylinder feels in the water, but material itself is not a direct SAC input here.
The surface-normalisation method is the same. In the real-gas model, oxygen percentage changes the gas-property correction slightly, which is why gas mix is included as an input.