How to Calculate Your SAC Rate and Improve Gas Efficiency

Dan Johnson
Feb 22
2 min read

Updated: Apr 1

Calculate Your SAC Rate for better Air Consumption — Calculate your SAC Rate to improve your Air Consumption

Every diver talks about air consumption.Very few actually understand it.

If you want longer dives, safer gas planning, and better control — you need to understand your SAC rate.

What Is SAC Rate?

SAC stands for Surface Air Consumption.

It tells you how much air you breathe per minute at the surface (1 bar / 1 ATA).Because pressure increases underwater, your gas usage increases proportionally with depth.

Knowing your SAC rate allows you to:

Plan dives more accurately
Predict gas needs for deeper dives
Improve safety margins
Track breathing efficiency
Reduce stress and unnecessary gas waste

How to Calculate Your SAC Rate

You need:

Starting tank pressure
Ending tank pressure
Dive time
Average depth
Tank volume (liters)

Step 1: Calculate Air Used

Example:

Start pressure: 200 bar
End pressure: 120 bar
Tank size: 12L

Air used:

(200 – 120) × 12 = 960 liters

Step 2: Calculate Ambient Pressure at Depth

Average depth: 20 meters

Ambient pressure formula:

(Depth ÷ 10) + 1

(20 ÷ 10) + 1 = 3 ATA

Step 3: Calculate SAC Rate

Dive time: 40 minutes

SAC formula:

Air Used ÷ (Time × Ambient Pressure)

960 ÷ (40 × 3) = 8 liters per minute

That means at the surface, you consume 8 liters per minute.

What Is a Good SAC Rate?

20+ L/min → High consumption
15–18 L/min → Average recreational diver
10–14 L/min → Good control
Below 10 L/min → Very efficient

Efficiency improves with:

Better buoyancy
Trim control
Calm breathing
Reduced task loading
Proper weighting

Why SAC Rate Matters for Deeper or Nitrox Diving

When diving deeper wrecks like the Bremen or HTMS Kut, gas planning becomes critical.

At 30 meters, you are breathing 4 times your surface consumption.

If your SAC is 15 L/min at surface:

At 30m → 15 × 4 = 60 L/min

That’s a huge difference.

Without knowing your SAC rate, you’re guessing.

And guessing underwater is not professional dive planning.

Improving Your Gas Efficiency

Here’s what actually works:

• Slow down your kick cycle• Improve trim to reduce drag• Use frog kick instead of constant flutter• Reduce hand movement• Focus on slow, controlled breathing• Dive more frequently

Gas efficiency is not about “holding your breath” — it’s about control and relaxation.