Calculate geodesic dome strut lengths, hub angles, and triangle counts for 2V and 3V frequency domes.
Enter the dome radius in feet and choose a frequency. Frequency describes how finely the underlying icosahedron is subdivided: a 2V dome uses two strut lengths, while a 3V dome uses three shorter ones and approximates a sphere more closely.
For a 2V dome the calculator returns strut A = 0.6180 × radius and strut B = 0.5465 × radius. A 10 ft radius therefore needs A struts of 6.18 ft and B struts of about 5.47 ft.
A 3V dome uses chord factors 0.34862, 0.40355, and 0.41241 for struts A, B, and C — all roughly a third shorter relative to the radius than the 2V lengths. The floor area is πr² in square feet: about 314 sq ft at 10 ft radius, 707 sq ft at 15 ft.
Frequency. A 2V dome subdivides each icosahedron edge twice, producing two unique strut lengths (0.6180r and 0.5465r); a 3V dome subdivides three times, producing three unique lengths between 0.34862r and 0.41241r. More, shorter struts make the 3V shell smoother and rounder.
Linearly. Each strut is a fixed chord factor multiplied by the radius, so doubling the radius doubles every strut. A 2V strut A goes from 6.18 ft at a 10 ft radius to 12.36 ft at 20 ft, with no change in the geometry of the joints.
The calculator reports the circular footprint πr². A 12 ft radius covers about 452 sq ft and a 16 ft radius about 804 sq ft — though headroom shrinks toward the curved wall, so usable area is somewhat less than the raw footprint.
The letters follow the chord-factor tables, not a size order. In the 2V table A = 0.6180r exceeds B = 0.5465r, while the 3V factors run A = 0.34862r, B = 0.40355r, C = 0.41241r. Always sort your cut list by the reported lengths, not by letter.