Scuba Air Consumption (SAC) Calculator
Turn a real dive into a surface air consumption rate you can reuse for gas planning. Enter how much pressure you used, over how long and at what depth, and the result is normalised back to the surface so different dives compare fairly.
How to calculate your SAC rate
- Note your cylinder pressure at the start and end of a steady-depth segment.
- Enter the pressure used, the time in minutes and the average depth.
- Read your surface air consumption rate in pressure per minute and log it.
Examples
Imperial dive in psi
3000 to 1500 psi, 20 min, 66 ft
ata 3.0, used 1500 psi, SAC 25 psi/min
Metric dive in bar
200 to 100 bar, 25 min, 20 m
ata 3.0, used 100 bar, SAC 1.33 bar/min
Frequently asked questions
What is surface air consumption?
SAC is how much cylinder pressure you breathe per minute when normalised to the surface. Because it removes the effect of depth, you can use one SAC rate to estimate gas use at any planned depth.
How is the SAC rate calculated?
Find ambient pressure: ata is depth in metres over 10 plus 1, or depth in feet over 33 plus 1. Pressure used is start minus end. SAC is pressure used divided by (minutes times ata).
Does it work in psi or bar?
Both. The maths is unit agnostic, so feed psi to get a psi per minute rate or bar to get a bar per minute rate. Just keep start and end pressure in the same unit.
Why divide by ata?
At depth each breath holds more gas, so raw pressure use overstates your real rate. Dividing by the ambient pressure in ata scales it back to the surface, where rates from different dives line up.
Can I plan gas with this alone?
No. This is a training and planning aid only. Get certified, build in a generous reserve and rock-bottom gas, follow your training and defer to your dive computer and gauges underwater.
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Equivalent Air Depth Calculator
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