About BikeFit

BikeFit is an independent, browser-based collection of bike fit and bike sizing calculators. It helps riders find a practical starting point for saddle height, frame size, riding position and bike geometry comparison before visiting a professional bike fitter.

What the tools do

Each calculator turns a few simple body measurements — height and inseam, plus optional torso, arm and shoulder values — into a concrete starting setup: a likely frame size, a starting saddle height, a position profile and step-by-step fine-tuning guidance. The geometry comparison tool lets you compare stack, reach and other key measurements between two bikes. Every calculation runs entirely in your browser; nothing is uploaded to a server.

How the estimates are built

Every formula on this site is a documented convention from the bike-fitting and cycling-biomechanics literature, implemented as written and cited on each tool page:

• Saddle height uses the inseam × 0.883 convention (bottom-bracket center to saddle top along the seat tube), a starting-point formula of the kind evaluated in the peer-reviewed saddle-height literature. It is deliberately presented with a tuning window, never as a final value.
• Knee-angle context comes from the clinical fitting literature: the Holmes method's 25–35° knee-flexion window at the bottom of the pedal stroke is the standard reference a fitter would check your result against.
• Frame sizing maps height and inseam onto generic industry size bands; when the two disagree, the tool reports a between-sizes result instead of hiding it.
• Stack and reach are used as defined by the fitting industry — the vertical and horizontal distances from bottom bracket to the top of the head tube — the standard metrics for comparing fit across brands.

Sources we build on

• Holmes, Pruitt & Whalen (1994), Lower extremity overuse in bicycling, Clinics in Sports Medicine — the knee-angle fitting reference. PubMed 8111852
• Gatti et al. (2022), Equations to prescribe bicycle saddle height, European Journal of Sport Science — how inseam, seat-tube angle and target knee angles relate. PubMed 33691592
• Visentini & Stewart (2022), Factors associated with overuse injury in cyclists: a systematic review, Journal of Science and Medicine in Sport — the evidence base for what bike fit can and cannot claim. PubMed 35151569
• Slowtwitch Stack & Reach Primer (Dan Empfield) — industry-standard frame-comparison metrics. slowtwitch.com
• Brand size charts (Specialized) link the manufacturer's official size guide and show the date each chart was verified.

What the evidence does and does not support

We deliberately avoid claims the literature does not support. A 2022 systematic review (Visentini & Stewart) found no strong evidence linking any single bike-fit measurement to overuse injury outcomes — so this site presents its numbers as defensible starting points to test on the bike, not as injury cures or guarantees of comfort. If discomfort persists, the evidence-backed answer is a qualified bike fitter or clinician, not another calculator.

Editorial standards

Formulas are fixed, documented and cited on every tool page. Brand-specific charts carry a verification date and a link to the manufacturer's official guide, because size bands change between model years. Content is written against the cited sources; when a convention is contested in the literature, the tool page says so. Results always state what they cannot measure: flexibility, pedaling style, injury history and the specific bike in front of you.

Who operates it

BikeFit is operated as an independent web product. It is not affiliated with, sponsored by or endorsed by any bicycle manufacturer or fitting school. Brand names such as Specialized appear only to describe size-chart lookup needs and are the property of their respective owners.