Because they measure different things — PSI is pressure, CFM is airflow volume. There is no conversion formula.
When selecting or evaluating a compressed air system, two specifications appear everywhere: CFM and PSI. They often sit side by side on compressor datasheets, but they describe completely different characteristics of compressed air. Because of this, CFM and PSI cannot be converted into each other, even though they interact closely in real system performance.
Understanding what each unit represents is essential for choosing the right compressor and avoiding misleading assumptions about its capacity.
What CFM Really Measures
CFM — Cubic Feet per Minute — expresses the volume of air a compressor delivers each minute.
It is an airflow measurement and reflects how much air is available to power tools or processes.
Internal “Air Theory” resources define airflow as the delivered volume of air at the compressor’s actual inlet or site conditions, which is why CFM varies with pressure, temperature and humidity.
This makes CFM the key value when determining whether a compressor can supply enough air for an application.
What PSI Really Measures
PSI — Pounds per Square Inch — expresses pressure, not airflow.
Pressure indicates the force with which the air is delivered.
Compressed air guides emphasise that different processes and tools require different PSI levels to function correctly. PSI determines whether the air has enough force to perform the task, while CFM determines whether there is enough volume to keep the tool running.
Why You Can’t Convert CFM Into PSI (Or PSI Into CFM)
CFM and PSI are related during compressor operation — when pressure increases, volume decreases — but they are not convertible units. They measure different physical properties:
- CFM = flow rate
- PSI = pressure
Internal compressor selection guides explicitly state that CFM and PSI cannot be converted, because airflow and pressure act independently and serve different system requirements.
A change in pressure affects how much air a compressor can supply, but that does not create a mathematical conversion. It only changes the system’s relationship between force and volume.
How CFM and PSI Work Together
While they cannot be converted, CFM and PSI must always be considered together:
- PSI determines the force needed for a task
- CFM determines the air quantity needed to keep the task running
Tools like impact wrenches, spray guns, grinders, and blow‑off equipment list both requirements: for example, 90 PSI and 5 CFM. The compressor must meet both values at the same time for the tool to operate correctly.
Common Misunderstanding: “More PSI = More CFM”
Raising PSI does not increase CFM.
In fact, higher pressure usually requires more power and reduces the available volume of free air unless the compressor is sized for it.
Airflow definitions in internal “Air Theory” material make this clear: pressure changes directly affect air density, not compressor displacement.
Frequently Asked Questions
No. Increasing PSI does not create more airflow; it only increases the pressure. Actual delivered flow depends on compressor displacement and conditions.
Neither on its own. Tools require both a specific airflow and pressure to operate correctly, so both numbers must be matched to the application.
