Bike Fit Calculator

Recommended Frame Size responds to exactly one input — Inseam Length. It uses a standover-clearance formula (inseam x 0.7, minus 2 cm) common in road-bike sizing charts, so Torso Length, Arm Length, and Height have zero effect on this number no matter how much they change. Those other three measurements instead drive different, independent outputs: Torso Length and Arm Length combine into Effective Reach (their sum x 0.47, a rough proxy for how stretched-out your position should be), while Height alone sets Stack (height x 0.34), the vertical dimension of the front end. Saddle Height uses the Hamley formula — inseam x 0.883, a widely cited road-cycling rule of thumb measuring bottom-bracket to saddle-top — that many fitters use as a starting point before fine-tuning by feel.

Handlebar Drop is estimated as 10% of Saddle Height, a starting-point figure from published road-bike-fit methodology (real fits typically run about 1 cm higher for a relaxed position or 1 cm lower for an aggressive one), so like Saddle Height it rises and falls with Inseam Length alone — across the full Inseam Length range it lands between roughly 5.3 and 8.8 cm, with a 2-12 cm clamp as a defensive sanity bound for unrealistic inputs rather than the thing driving the everyday result. Estimated Stem Length and Crank Length Recommendation are similarly rough: stem length derives from reach and frame size algebraically, while crank length steps between four fixed lengths (165-175 mm) based on inseam brackets rather than a continuous formula. None of these numbers replace a professional bike fit — they are starting points for adjustment, not final measurements, and the calculator has no way to account for flexibility, riding style, or injury history.