// multi-utility computation suite · offline · instant · precise
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eng.duct-pressure-loss-equal-friction Calculator
Calculates ductwork pressure loss using the equal friction method from air flow, friction rate, and duct material roughness. The equal friction method sizes all ducts to the same pressure drop per metre — it's the most common HVAC duct sizing approach.
Inputs
Q L S
Reference formula or conversion factor shown for context.
D Mm
Distance across a circle through its centre. Always confirm units match the rest of the calculation.
L M
Linear measurement. Ensure consistent units: 1 m = 1,000 mm = 3.281 ft.
Roughness Mm
Reference formula or conversion factor shown for context.
Results
pressure drop ΔP (Pa)
Pressure lost to friction as fluid moves through the pipe or system. Higher drop = more pumping power required. Reduce by using larger pipes, fewer bends, or lower flow velocity.
air velocity V (m/s)
Reference formula or conversion factor shown for context.
friction factor f (Swamee-Jain)
A dimensionless multiplier applied in the calculation.