CFM vs L/min Explained — What Air Compressor Specs Actually Mean

Air compressor specifications can be confusing — especially when different manufacturers use different units. CFM, L/min, FAD, Bar, PSI, max displacement — what does it all actually mean? This guide explains every key air compressor specification in plain English so you can make a confident buying decision.

CFM — Cubic Feet per Minute

CFM measures the volume of air a compressor delivers per minute. It's the most important performance figure for matching a compressor to your tools because your tools need a minimum CFM to operate properly.

There are two CFM figures you'll see:

Max displacement CFM — the theoretical maximum the pump can move under no load and no pressure. This is the best-case figure and not what your tools actually receive.

FAD CFM (Free Air Delivery) — the actual volume of air delivered at a specific working pressure. This is the honest, real-world figure. Always use FAD when comparing compressors to your tool requirements.

Example: The TEH TAC50L has a max displacement of 14.8 CFM but a FAD of 8.5 CFM at 6 Bar and 7.0 CFM at 8 Bar. The FAD figures are what matter for running your tools.

L/min — Litres per Minute

L/min is simply CFM expressed in metric units. They measure the same thing — the volume of air delivered per minute.

To convert: 1 CFM = approximately 28.3 L/min

So 7.0 CFM = approximately 200 L/min. UK manufacturers often use L/min while US manufacturers tend to use CFM — now you know they're the same measurement in different units.

FAD — Free Air Delivery

FAD is the most honest and useful airflow figure. It tells you the actual volume of usable air the compressor delivers at a specific pressure under real working conditions — accounting for heat, friction, and mechanical losses.

Always look for FAD figures at the pressure you'll actually be working at. Most tools operate between 5-8 Bar so check the FAD at 6 Bar and 8 Bar when comparing compressors.

Bar and PSI — Pressure

Bar and PSI both measure air pressure — they're just different units.

1 Bar = 14.5 PSI

Most UK pneumatic tools operate between 5-8 Bar (72-116 PSI). Most TEH compressors have a maximum pressure of 8 Bar (116 PSI) which covers the full range of standard pneumatic tools.

Higher pressure isn't always better — running tools at higher pressure than they need wastes air and shortens tool life. Match your compressor output pressure to your tool's recommended operating pressure.

Tank Size — Litres

The tank stores compressed air as a buffer between the motor cycling and your tool demand. A larger tank means:

• More reserve air for burst demand tools like impact wrenches
• Less frequent motor cycling for extended continuous use
• More consistent pressure during heavy use

Tank size does NOT determine how much air the compressor produces — that's determined by the motor and pump (FAD). A large tank with a weak pump will still starve a high-demand tool.

HP — Horsepower

HP indicates the motor power. More HP generally means more airflow capacity. Our range goes from 2HP (TAC24L) through 2.5HP, 4HP (TAC50L twin motor), 6HP (TAC100L triple motor) to 8HP (TAC130L quad motor).

Duty Cycle

Some compressors are rated for intermittent use and need rest periods. Most TEH oil-free compressors are designed for continuous professional use — check the product specifications if duty cycle is important for your application.

Quick Reference — TEH Tools Compressor Specs:

The Bottom Line

When buying an air compressor always check:

1. FAD at working pressure — not max displacement
2. FAD must exceed your tool's CFM/L/min requirement
3. Tank size for your usage pattern
4. Noise level if working indoors or in residential areas

Browse our full compressor range at tehtools.co.uk