Closed Pipe Organ Length Calculator

Organ pipe length from frequency: formula and example

Acoustically, flue organ pipes fall into two families. An open pipe (both ends open) follows f = v / (2L), while a stopped pipe (one end closed) follows f = v / (4L). Builders treat the 8' rank as the reference point. An open eight-foot pipe runs about 2.56 m and speaks at keyboard pitch, with its lowest C landing near 64 Hz. Double that length and you get a 16' rank, an octave lower. Push it further and you reach the monstrous 64' stop found in a handful of cathedral organs, which bottoms out around 8 Hz, infrasound that you feel more than you hear.

Context and applications

When a builder lays out a rank, the formula gives the starting length and the voicing at the mouth handles the fine tuning afterward. Hauptwerk and similar virtual pipe-organ samplers reproduce that same scaling in software. Because a stopped pipe (Gedackt, Bourdon) sounds an octave below an open pipe of the same length, organ makers use them to save both space and metal. Even the Wagner tuba, despite being brass, relies on the same half-wavelength resonance in its bore.

FAQ

Why is a stopped pipe half the length? The closed end pins a velocity node, so only a quarter wavelength fits inside: λ = 4L. You get the same pitch from half the pipe, though only odd harmonics survive, which is why the tone comes out hollow.

What does the "foot" notation mean? An 8' (eight-foot) rank plays at written pitch. A 4' rank sits an octave above, a 16' an octave below. The number roughly equals the length in feet of the lowest open C pipe.

Can humans hear a 64' rank? Not really the fundamental. At ~8 Hz it falls below the ~20 Hz floor of human hearing. What you do catch are its harmonics and the beating it sets up against other ranks. The rest registers as a physical rumble in your chest and the chapel walls.