Size a low-pressure gas run: enter the flow, length and allowed pressure drop, and see the drop and velocity for each standard pipe diameter — with the smallest passing size highlighted. Or check one specific diameter.
The Renouard linear formula, the standard low-pressure sizing method referenced by EN 12007-family practice and national codes (French DTU 61.1, Spanish UNE 60670):
ΔP (mbar) = 23200 · d · L · Q1.82 / D4.82
with d the gas relative density (0.6 natural gas, 1.56 propane, 2.01 butane), L the equivalent length in meters (add ~20% for fittings if you have not counted them), Q in m³/h and D the internal diameter in mm. Valid for operating pressure below ~100 mbar and Q/D < 150. Velocity shown is at near-atmospheric pressure; keep it under ~6 m/s indoors (20 m/s for mains) to avoid noise and dust pickup.
Design aid, not a substitute for the code. Real installations must be sized and approved by a qualified installer against the applicable national regulations and the actual fitting layout. Internal diameter, not nominal size, is what the formula uses.