Calculate the required compressor Free Air Delivery from your tool demand, duty cycle, leakage and safety margin.
Sum of all tools that may run simultaneously
% of time compressor runs under load
Typical: 5–15% for older systems
Headroom for future tools (typically 20%)
Enter tool demand to calculate required compressor size.
Required = (Demand × (1 + leakage) ÷ duty cycle) × (1 + safety factor). FAD = Free Air Delivery at atmospheric pressure.
Add up the air demand of all tools that may run at the same time. Apply a duty cycle (how often the compressor runs under load — typically 70%), add a leakage allowance (10–15% for older systems), then add a 20% safety factor for future growth. The result is your required Free Air Delivery (FAD).
FAD (Free Air Delivery) is the volume of air delivered by a compressor measured at atmospheric pressure conditions. It is the most common way to rate compressor output and allows direct comparison between models. Always match tool demand in FAD L/min to compressor output in FAD L/min.
A 70% duty cycle is a common starting point for industrial compressors. This means the compressor runs under load 70% of the time and is unloaded or stopped the remaining 30%. Single-phase compressors may use 50–60%. Running a compressor above its rated duty cycle shortens its life.