Pump-up Test CFM: Measuring Output Based on Fill Time

Pump-up test calculators help estimate the actual air output (in cubic feet per minute, or CFM) of your compressor based on how long it takes to fill a tank. This is a practical way to assess performance without the need for specialized flow meters—perfect for diagnostics, comparisons, and long-term tracking.

What This Calculator Helps You Do

• Estimate your compressor’s actual CFM output
• Compare real-world performance to manufacturer specs
• Diagnose issues related to leaks, wear, or mechanical inefficiencies
• Evaluate whether your compressor is still sized properly for your needs
• Track historical performance as part of preventative maintenance

How to Use This Calculator

This calculator requires the following inputs:

• Tank Volume (gallons)
• Start Pressure (cut-in PSI)
• Stop Pressure (cut-out PSI)
• Pump-up Time (minutes)

It estimates CFM output using this formula:

• CFM = (Tank Volume × ΔP) / (7.48 × 14.7 × Pump-up Time)

Where ΔP is the difference between cut-out and cut-in pressure.

This provides an estimate of SCFM (standard cubic feet per minute), assuming sea-level conditions and no losses. While it's not exact, it’s useful for performance comparisons and ongoing monitoring.

When to Use This Calculator

• After installing a new compressor
• To confirm sizing before purchasing a new compressor or tank
• During maintenance to monitor changes in output
• If your air tools or systems feel underpowered
• To validate performance on used equipment
• To troubleshoot declining performance or slow pressure recovery
• When increasing demand for air in your shop
• After changing key components like check valves, belts, or switches

What the Result Tells You

Your result is an estimate of your compressor’s output CFM under current operating conditions. If this number is within 5–10% of your rated output, your system is likely performing well.

If the result is significantly lower, you may be experiencing issues such as:

• Air leaks in lines, fittings, or the tank
• Worn valves or piston rings inside the compressor
• Dirty air filters or flow restrictions
• Incorrect cut-in/cut-out pressure settings
• Slipping or misaligned belts in belt-driven models

Monitoring this metric regularly helps detect early signs of wear or performance drop-off. If your system can’t keep up despite proper maintenance, it may be time to upgrade to a higher CFM model.

Explore our full lineup of replacement air intake filters and silencers, and rebuild kits to improve efficiency and shorten fill times. Or call us at 402-261-9563 for help selecting the right compressor or pump for your needs.

Visit our resource library to see all calculators and other resources.

Disclaimer: This calculator is provided for general informational purposes only. While we strive for accuracy, results depend on the information you enter and may not reflect all real-world conditions. This tool and any related materials are provided “as-is” without warranties of any kind. Always verify measurements and specifications before purchasing, installing, or operating equipment. We are not responsible for any damages or issues arising from use of this information.