Preview v524View your fit
Your height and a frame. See where your body ends up before you buy it.
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The next question is always which of two. One rider, four bikes; pick any of them and the others are measured against it.
What it does not do
It is static geometry, not pedalling motion. It will not tell you whether your knee hurts. It is not a replacement for a fitter with their hands on you; it is the picture you both look at before and after.
Every number on screen says where it came from. A frame's geometry is the maker's own chart or it is marked pending and left out of sizing. Joint windows are the ranges fitters publish, named on the how it works page, and they are a starting point, not a verdict.
Who it is for
Questions
The defaults follow mainstream road-fitting conventions: saddle height is calibrated so that a 145 degree knee angle corresponds to the classic 0.883 times inseam rule, KOPS is drawn as a reference plumb line rather than enforced as a rule, and the hip joint centre sits 78mm above the saddle by default, within the anatomical seated range. Joint angles update live so you can check them against whichever school of fitting you follow. It is a planning and visualisation tool. A professional bike fit assesses your flexibility, injury history and asymmetries on a real bike, Use it to prepare for that fit, not instead of it.
From the same definitions manufacturers use in their published charts. Stack and reach are measured from the bottom bracket to the top of the head tube; trail is derived as (wheel radius times cosine of the head angle, minus rake) divided by sine of the head angle; wheelbase, front-centre, effective top tube and standover all follow from the solved frame. Because the whole frame is parametric, every derived value updates the moment you move a slider, and you can check the tool against any brand's chart by entering their numbers.
With an account, your library is stored securely online and is available wherever you sign in. The number of saved profiles, configurations and measurements you can keep depends on your plan; the table above sets out the limits for each tier.
