A/B/C/D convention: A/B are flange PCD, C/D are center-to-flange spacing. A and C are the right side of the bike (the drive side on rear wheels); B and D are the left side (non-drive; also the rotor side on disc hubs). Fields and results are laid out to match the bike: left side on the left, right side on the right. For front, symmetric wheels, A=B and C=D. For rear or disc hubs, the two sides are usually different — that's the dish.

Rounding: the default increment is 1mm, suited to custom-cut spokes and to ranges (Sapim, DT Swiss and others) available in 1mm steps — odd lengths are valid results. Switch to 2mm (even stock sizes) if buying from stock that only carries even lengths. The default rounds down: this calculator computes pure geometric length with no spoke-stretch correction, so the raw figure runs slightly long relative to the tensioned wheel — rounding down compensates, and a slightly short spoke won't bottom the nipple on the unthreaded shank. Raw unrounded values are always shown beneath each readout.