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Pressure drop calculations in compressed air pipelines
Compressed air pressure drop calculator
Professional calculator for computing pressure drops in compressed air pipelines. Calculations use an empirical formula widely applied in the pneumatics industry (referenced in Atlas Copco and Kaeser manuals), taking into account FAD volumetric flow rate, internal pipe diameter, section length and working pressure.
Designed for pneumatic system designers, compressor service engineers and maintenance professionals. The calculator supports three pipe series (plastic, aluminium, press-fit steel) and allows manual entry of a custom internal diameter. Calculations can be performed section by section — the result is the total pressure drop across the entire installation.
How to use the calculator in 3 steps
Select the pipe type (plastic, aluminium, press-fit steel) and the appropriate diameter from the predefined series. If your pipe does not match any series, choose "Custom diameter" and enter the internal diameter manually.
Enter the air flow rate in m³/min (FAD — Free Air Delivery, i.e. flow converted to atmospheric conditions) and the initial pressure at the section inlet (default 8 bar).
Enter the pipe section length in metres. Add more sections with the "Add row" button — the calculator automatically sums the pressure drops from all sections.
What the calculator computes
For each installation section the calculator determines:
- dP — pressure drop per section [bar], calculated from the empirical formula accounting for flow, diameter, length and working pressure.
- Σ dP — total pressure drop across the entire installation, being the sum of drops across individual sections. The recommended total pressure drop should not exceed 0.1 bar (1% of working pressure at 10 bar).
- Design verification — with correct sizing, air velocity in main pipes should be 6–8 m/s and up to 15 m/s in branches.
Input data — what to enter and where to find it
Pipe type
Select the pipe material and system. Aluminium pipes (e.g. Aircom) are currently the most popular choice — lightweight, corrosion-resistant, with a smooth internal surface that minimises losses. Press-fit steel pipes are suitable for industrial installations. Plastic pipes (PVC) — caution: do not use standard PVC for compressed air due to the risk of brittle fracture under pressure! Only systems specifically designed for compressed air are acceptable.
Pipe diameter [mm]
The internal pipe diameter (ID) determines the pressure drop — even a small diameter increase drastically reduces losses (d⁵ dependency). After selecting a pipe series, the available diameters load automatically. With the "Custom diameter" option, enter the internal diameter manually.
Flow rate [m³/min]
Volumetric air flow expressed as FAD (Free Air Delivery) — flow converted to atmospheric conditions (1 bar abs., 20°C). The FAD value can be found in the compressor data sheet. Note: do not confuse with displacement, which is 10–30% higher than FAD depending on compressor efficiency.
Initial pressure [bar]
Gauge pressure at the start of the calculated section. Typical working pressures: 7–8 bar in industrial installations, 6–8 bar in workshops, up to 13 bar for special applications. Default value in the calculator is 8 bar.
Pipe length [m]
Actual length of straight pipe in metres. Remember to add equivalent lengths for fittings — each 90° elbow adds approx. 0.5–1.5 m (depending on diameter), a tee adds 1–3 m, and a ball valve 0.1–0.5 m. In practice, add 30–50% to the measured pipeline length for fittings.
Calculation formula
The calculator uses an empirical formula widely applied in the pneumatics industry, published in Atlas Copco, Kaeser and SMC manuals:
- dp — pressure drop [bar]
- q — FAD volumetric flow [m³/min]
- L — pipe length [m]
- d — internal pipe diameter [mm]
- p — initial gauge pressure [bar]
Design tips
The recommended total pressure drop in an installation should not exceed 0.1 bar (at 8–10 bar working pressure). Every 1 bar of excessive pressure drop increases compressor energy consumption by approx. 7%. When designing, account for fittings — add 30–50% equivalent length to the measured pipeline length. Use a ring layout instead of dead-end branches — a ring provides supply from two directions and reduces the pressure drop by approx. 50% compared to a single-sided branch.
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Want to learn the theory and design principles?
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Compressed air installation — design, calculations and pipe sizing