What is a normal SAC rate?

A typical SAC rate for an average recreational diver is 15-20 L/min (0.5-0.7 cuft/min). Beginners often see 20-30 L/min, while experienced divers can achieve 10-15 L/min. Your SAC rate naturally improves with diving experience.

Why does my SAC rate change from dive to dive?

SAC rate varies based on exertion level, water temperature, stress, current, visibility, equipment fit, and even your mood. Cold water, strong currents, and unfamiliar environments all increase air consumption. Track your SAC over many dives to find your average.

Should I use SAC or RMV for gas planning?

Both work for gas planning since they express the same concept — your surface-normalized consumption rate. SAC is more commonly used in recreational diving, while RMV is prevalent in technical diving. The key is consistency: pick one method and use it for all your planning.

Understanding SAC Rate: Why It Matters for Every Diver

Surface Air Consumption (SAC) rate is one of the most important metrics in scuba diving. It tells you how much breathing gas you consume per minute at surface pressure, giving you a depth-independent measure of your gas efficiency. Knowing your SAC rate is essential for gas planning, safety, and becoming a better diver.

What Exactly is SAC Rate?

When you dive deeper, the ambient pressure increases and you consume gas faster. At 10 meters, the ambient pressure is 2 ATA, so you breathe gas at twice the surface rate. At 20 meters, three times. SAC rate removes this depth effect by normalizing your consumption back to surface-equivalent values.

This makes SAC rate a consistent personal metric. Whether you dove to10m or 30m, your SAC rate should be roughly the same (assuming similar conditions and exertion). This consistency is what makes it useful for planning future dives at any depth.

How to Calculate SAC Rate

To calculate your SAC rate, you need four pieces of information from your dive:

Starting tank pressure — what your gauge read before the dive
Ending tank pressure — what your gauge read after the dive
Average depth — most dive computers record this
Dive time — total time from descent to ascent

The SAC Rate Formula

\text{SAC} = \frac{P_{\text{start}} - P_{\text{end}}}{t \times D_f}

Where $D_f$ is the depth factor that converts actual consumption back to surface pressure:

D_f = \frac{\text{depth (m)}}{10} + 1 \quad \text{or} \quad \frac{\text{depth (ft)}}{33} + 1

This gives you SAC in bar/min — the rate of pressure drop per minute at the surface.

Worked Example

You dive for 40 minutes at an average depth of 15 meters. Start pressure: 200 bar. End pressure: 80 bar. Tank: 12L.

Depth factor = 15/10 + 1 = 2.5 ATA

SAC = (200 - 80) / (40 x 2.5) = 120 / 100 = 1.2 bar/min

RMV = 1.2 x 12 = 14.4 L/min

Try it: SAC Rate Calculator

Start Pressure (bar)End Pressure (bar)Avg Depth (m)Dive Time (min)

Tank

SAC: 1.2 bar/min|RMV: 14.4 L/min

Personal rates vary by conditions and dive workload.

What is a Good SAC Rate?

There is no universal "good" or "bad" SAC rate that applies to every diver or every dive. Your gas use changes with conditions, workload, equipment setup, and how comfortable you are in that environment.

A calm, warm, low-current reef dive can produce a much lower SAC than a cold dive in current with task loading, thick exposure protection, or stress. That does not automatically mean one number is "good" and the other is "bad".

How to judge your SAC usefully

Compare SAC against your own dives in similar conditions, not against other divers.
Track trends over time: stability and improved control matter more than a single low number.
Plan gas with conservative assumptions for the hardest part of the dive, not your best-case SAC.
Use SAC as a planning tool and safety metric, not as a scorecard.

Tips to Improve Your SAC Rate

Master your buoyancy. Poor buoyancy leads to constant adjustments, extra finning, and wasted energy. Achieving neutral buoyancy means less effort and lower gas consumption. Practice hovering motionless at a fixed depth.
Breathe slowly and deeply. Shallow, rapid breathing is inefficient because more air stays in your dead space (airways) without participating in gas exchange. Slow, deep breaths maximize oxygen uptake and minimize wasted gas.
Streamline your equipment. Dangling hoses, loose accessories, and poor trim create drag. More drag means more effort to move through the water, which means more gas consumed.
Stay calm and relaxed. Anxiety, stress, and excitement all increase breathing rate and gas consumption. Experience and familiarity with your environment naturally reduce stress over time.
Track your progress. Log your SAC rate after every dive. Tracking trends over time helps you understand what conditions affect your consumption and measure your improvement.

Ready to calculate your SAC rate? Use our free SAC Rate Calculator to quickly determine your surface consumption rate from your last dive data. Want to go further and convert your SAC to RMV? Try the SAC Rate & RMV Calculator or read our guide on SAC vs RMV differences.