Surface Air Consumption Rate Formula

SAC Rate Formula:

\[ SAC = \frac{(Starting\ PSI - Ending\ PSI) \times Tank\ CF}{Dive\ Time \times Avg\ Depth\ (ATA)} \]

Starting PSI:

psi

Ending PSI:

psi

Tank CF:

cubic feet

Dive Time:

minutes

Avg Depth:

ATA

SAC Rate:

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1. What is Surface Air Consumption Rate?

The Surface Air Consumption (SAC) rate measures a diver's air usage at the surface, expressed in psi per minute. It helps divers plan their dives and estimate how long their air supply will last at different depths.

2. How Does the Calculator Work?

The calculator uses the SAC rate formula:

\[ SAC = \frac{(Starting\ PSI - Ending\ PSI) \times Tank\ CF}{Dive\ Time \times Avg\ Depth\ (ATA)} \]

Where:

\( Starting\ PSI \) — Initial tank pressure in pounds per square inch
\( Ending\ PSI \) — Final tank pressure in psi
\( Tank\ CF \) — Tank capacity in cubic feet
\( Dive\ Time \) — Total dive duration in minutes
\( Avg\ Depth \) — Average depth in atmospheres absolute (ATA)

Explanation: The formula calculates air consumption at surface pressure by accounting for the actual depth during the dive through the ATA conversion.

3. Importance of SAC Rate Calculation

Details: Knowing your SAC rate is crucial for dive planning, ensuring you have enough air for the planned dive profile, and for comparing air consumption efficiency between dives and divers.

4. Using the Calculator

Tips: Enter starting and ending tank pressure in psi, tank capacity in cubic feet, dive time in minutes, and average depth in ATA. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a good SAC rate?
A: A SAC rate of 0.4-0.7 psi/min is typical for recreational divers. Lower rates indicate better air consumption efficiency.

Q2: How do I convert depth in feet to ATA?
A: ATA = (Depth in feet / 33) + 1. For example, 66 feet = (66/33) + 1 = 3 ATA.

Q3: Why is SAC rate important for dive planning?
A: It helps calculate how long your air will last at planned depths and ensures you have sufficient air for the dive plus safety reserves.

Q4: What factors affect SAC rate?
A: Experience level, physical fitness, water temperature, current, workload, stress, and equipment configuration all influence air consumption.

Q5: How can I improve my SAC rate?
A: Practice buoyancy control, streamline equipment, move efficiently, stay relaxed, and maintain good physical fitness through regular exercise.