SAC Calculator
The SAC (Surface Air Consumption) calculator determines your gas consumption rate normalized to surface pressure. This value -- also known as RMV (Respiratory Minute Volume) -- lets you compare consumption across different dive profiles and plan gas requirements for future dives.
The SAC Calculator requires an active premium subscription.
Inputs
- Tank volume -- the physical size of your cylinder (in liters or cubic feet)
- Start pressure -- tank pressure at the beginning of the dive (in bar or psi)
- End pressure -- tank pressure at the end of the dive (in bar or psi)
- Average dive depth -- the average depth during the dive
- Dive time -- total dive duration in minutes
- Altitude -- elevation of the dive site
- Water type -- fresh or salt water
Full SAC calculator showing all input fields -- calc-sac-light.png / calc-sac-dark.png
Results
The calculator returns your SAC rate in both L/min and cuft/min, along with an interpretation of where your consumption falls:
| Rating | SAC Rate |
|---|---|
| Excellent | 12 L/min or less |
| Good | 12--16 L/min |
| Average | 16--20 L/min |
| High | Above 20 L/min |
SAC result displaying the rate in L/min and cuft/min with the consumption rating -- calc-sac-result-light.png / calc-sac-result-dark.png
How it works
SAC normalizes your actual gas consumption to what it would be at the surface (1 ATA). This removes the depth variable so you can compare consumption across dives at different depths. The formula accounts for ambient pressure at depth using the Buhlmann tissue model.
For example, if you consumed 80 bar from a 12 L tank over 40 minutes at an average depth of 20 m, the calculator first computes the total gas consumed, then divides by the ambient pressure factor at that depth and the dive duration to arrive at a surface-equivalent rate.
Knowing your SAC rate helps you plan gas consumption for future dives. A lower SAC means you'll have more gas available and longer bottom times. Track your SAC over multiple dives to get an accurate average.