To calculate the CFM (Cubic Feet per Minute) for an air compressor, follow these steps:
Preparation
1. Ensure your air compressor tank is empty.
2. Have a stopwatch or timer ready.
3. Note the volume of your compressor tank in gallons.
Calculation Process
Step 1: Convert Tank Volume
Convert the tank volume from gallons to cubic feet by dividing the gallon value by 7.48
Step 2: Measure Fill Time
Turn on the compressor and time how long it takes to fill the tank completely. Record the start and end pressures (PSI)
Step 3: Calculate Pressure Difference
Subtract the starting PSI from the ending PSI to get the pressure difference
Step 4: Convert Pressure
Divide the pressure difference by 14.7 to convert it to atmospheric pressure
Step 5: Calculate Air Volume
Multiply the converted tank volume (cubic feet) by the converted pressure difference.
Step 6: Determine CFM
Divide the air volume by the fill time in seconds, then multiply by 60 to get CFM
Formula
The simplified formula for CFM calculation is:
CFM = ((Tank Volume in cubic feet) * (Pressure Difference) * 60) / (Air Volume) * (Fill Time in seconds)
Example
Let's say you have a 24-gallon tank that fills from 0 to 160 PSI in 5 minutes:
1. Tank volume: 24 / 7.48 = 3.21 cubic feet
2. Pressure difference: 160 / 14.7 = 10.88 atm
3. Air volume: 3.21 × 10.88 = 34.92 cubic feet
4. CFM: (34.92 × 60) / (5 × 60) = 6.98 CFM
Therefore, this compressor has a CFM rating of approximately 7 CFM at 160 PSI.
Remember that actual CFM can vary based on factors like temperature and humidity, so this calculation provides an estimate of your compressor's performance.
