Dive Planning

SAC Rate Calculator

Calculate your Surface Air Consumption rate from dive data to improve gas planning and dive safety.

Dive data

SAC is a pressure rate, so these four readings are all it needs.

Starting Pressure

BAR

Ending Pressure

BAR

Dive Time

min

Average Depth

Convert to RMV

Your cylinder does not change the SAC rate above. It is needed to turn that pressure rate into a tank-independent RMV volume, so these values are carried over to the RMV calculator.

Tank Size

Tank Working Pressure

BAR

Calculate RMV with this cylinder

About SAC Rate

Surface Air Consumption (SAC) rate is how fast your cylinder pressure drops per minute, normalized to surface pressure. It is a key metric for gas planning, but because it is measured in pressure it stays tied to the cylinder you dived — convert it to RMV to compare across cylinders.

Formula:

\begin{aligned} \text{SAC} &= \frac{\Delta P}{t \, D_F} \\ \Delta P &= P_{\text{start}} - P_{\text{end}} \end{aligned}

Where:

• $\Delta P$ = pressure used in bar
• $t$ = dive time in minutes
• $D_F$ = depth factor = $\frac{Depth + 10}{10}$

Tips to Improve

• Perfect your buoyancy

Minimize unnecessary movements and finning

• Breathe continuously and comfortably

Never hold or deliberately restrict your breath to save gas

• Streamline your gear

Reduce drag and maintain proper trim

• Stay relaxed and calm

Stress and anxiety increase air consumption

Result

1.10 bar/min

Surface-normalized pressure use for the entered dive and cylinder.

Frequently Asked Questions

What is SAC rate in scuba diving?

In DiveCalc, SAC (Surface Air Consumption) is the cylinder-pressure drop per minute normalized to surface pressure, expressed in bar/min or PSI/min. Because it depends on the cylinder, convert it to RMV before comparing different cylinders.

What is a good SAC rate?

There is no universal pressure-based SAC value because bar/min or PSI/min depends on cylinder size and working pressure. Compare your own SAC on the same cylinder in similar conditions, or convert it to RMV for cross-cylinder comparisons. Use a conservative value for planning.

How do I calculate my SAC rate?

Subtract ending cylinder pressure from starting pressure, divide by dive time, then divide by the average ambient-pressure factor. The result is a surface-normalized pressure rate in bar/min or PSI/min. Cylinder size and working pressure are needed only when converting SAC to RMV.

What is the difference between SAC and RMV?

Terminology varies. DiveCalc uses SAC for surface-normalized cylinder pressure per minute and RMV for surface-equivalent gas volume per minute. SAC is cylinder-dependent; RMV can be used across cylinder configurations.

How can I improve my SAC rate?

Improve buoyancy, trim, streamlining, fitness, and comfort to reduce unnecessary workload. Breathe continuously and comfortably; never hold or deliberately restrict your breath to save gas. Track comparable dives and use conservative rates for planning.

Related Guides

Gas planning & consumption

Understanding SAC Rate: Why It Matters for Every Diver

Learn what Surface Air Consumption rate is, how to calculate it, and tips to improve your breathing efficiency underwater.

Gas planning & consumption

SAC Rate vs RMV: What's the Difference and When to Use Each

Understand the difference between SAC rate and RMV, when to use each metric, and how to convert between them.

Gas planning & consumption

How Long Will My Scuba Tank Last?

Estimate cylinder duration from usable gas, depth, and RMV, and understand why a constant-depth estimate is not a complete dive plan.

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