How To Calculate Air Compressor CFM

CFM Formula:

\[ CFM = \frac{Tank\ gal \times (Max\ PSI - Min\ PSI)}{14.7 \times Time\ min} \]

Tank (gallons):

gal

Max PSI (psi):

psi

Min PSI (psi):

psi

Time (minutes):

min

Free Air Delivery CFM:

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1. What Is CFM?

CFM (Cubic Feet per Minute) is a measurement of airflow volume that indicates how much air an air compressor can deliver at a specific pressure level. It's a crucial specification for determining the capability and performance of air compressors.

2. How Does The Calculator Work?

The calculator uses the CFM formula:

\[ CFM = \frac{Tank\ gal \times (Max\ PSI - Min\ PSI)}{14.7 \times Time\ min} \]

Where:

\( Tank\ gal \) — Air compressor tank capacity in gallons
\( Max\ PSI \) — Maximum pressure in pounds per square inch
\( Min\ PSI \) — Minimum pressure in pounds per square inch
\( Time\ min \) — Time in minutes to fill from min to max PSI
14.7 — Atmospheric pressure at sea level in PSI

Explanation: This formula calculates the free air delivery CFM by measuring how quickly the compressor can refill the tank from the minimum to maximum pressure.

3. Importance Of CFM Calculation

Details: Accurate CFM calculation is essential for selecting the right air compressor for specific tools and applications, ensuring adequate airflow for optimal performance and preventing compressor overload.

4. Using The Calculator

Tips: Enter tank capacity in gallons, maximum and minimum PSI values, and the time it takes to fill from min to max PSI. Ensure max PSI is greater than min PSI and all values are positive.

5. Frequently Asked Questions (FAQ)

Q1: What Is The Difference Between CFM And SCFM?
A: CFM measures actual airflow at specific conditions, while SCFM (Standard Cubic Feet per Minute) measures airflow at standard conditions (68°F, 0% humidity, sea level pressure).

Q2: Why Is 14.7 Used In The Formula?
A: 14.7 PSI represents atmospheric pressure at sea level, which is used to convert the compressed air volume to free air delivery equivalent.

Q3: What Is A Good CFM For Home Use?
A: For most home workshops, 5-10 CFM at 90 PSI is sufficient for common tools like nail guns, impact wrenches, and paint sprayers.

Q4: How Does Altitude Affect CFM?
A: At higher altitudes, atmospheric pressure decreases, which can reduce the actual CFM output of air compressors.

Q5: Can I Use This Calculator For Any Air Compressor?
A: Yes, this calculator works for all reciprocating and rotary screw air compressors with storage tanks, providing the free air delivery CFM measurement.