Air Compressor CFM Calculator

CFM Equation:

\[ CFM = \frac{Displacement \times RPM \times Vol_{Eff}}{1728} \]

CFM:

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1. What is Air Compressor CFM?

CFM (Cubic Feet per Minute) measures the volumetric flow rate of air delivered by a compressor. It indicates how much air the compressor can supply to power tools and equipment, making it a critical specification for compressor selection and performance evaluation.

2. How Does the Calculator Work?

The calculator uses the CFM equation:

\[ CFM = \frac{Displacement \times RPM \times Vol_{Eff}}{1728} \]

Where:

\( Displacement \) — Pump displacement in cubic inches (in³)
\( RPM \) — Rotational speed in revolutions per minute
\( Vol_{Eff} \) — Volumetric efficiency as a decimal (typically 0.7-0.9)
\( 1728 \) — Conversion factor from cubic inches to cubic feet

Explanation: The formula calculates the actual air delivery capacity by accounting for the compressor's physical displacement, operating speed, and efficiency losses.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is essential for matching compressors to air tools, ensuring adequate air supply, preventing system overload, and optimizing energy efficiency in pneumatic systems.

4. Using the Calculator

Tips: Enter displacement in cubic inches, RPM as specified for the compressor, and volumetric efficiency as a decimal (e.g., 0.85 for 85%). All values must be positive, with volumetric efficiency between 0 and 1.

5. Frequently Asked Questions (FAQ)

Q1: What is volumetric efficiency?
A: Volumetric efficiency represents how effectively the compressor pumps air compared to its theoretical maximum, accounting for factors like clearance volume, leakage, and valve losses.

Q2: What are typical volumetric efficiency values?
A: Most reciprocating compressors have volumetric efficiencies between 70-90%, with well-maintained units typically around 80-85%.

Q3: Why is the 1728 conversion factor used?
A: 1728 converts cubic inches to cubic feet (12³ = 1728), since displacement is typically in in³ while CFM is measured in ft³/min.

Q4: How does RPM affect CFM?
A: Higher RPM increases CFM proportionally, but excessive RPM can reduce efficiency and compressor lifespan due to increased heat and wear.

Q5: Can this calculator be used for all compressor types?
A: This formula is primarily for positive displacement compressors (reciprocating, rotary screw). Centrifugal compressors use different performance calculations.