Bike fit
Rider Inputs
Start with body measurements. The fitter uses them to set contact-point targets before scoring bike sizes.
Height and inseam required.
Use the saddle installed on the bike when you know it. If you do not, keep the default reference and treat setback as a starting coordinate to verify on the real saddle.
The rest of the body dimensions are estimated from your base inputs. Switch to detailed mode only if you can measure them cleanly.
How to Measure
A clean baseline starts with clean body numbers. Use the stage below to inspect any measurement freely, without locking the flow.
Stand barefoot with feet about 100-150 mm apart. Press a hardback book upward like a saddle, keep it level against the wall, and measure from the floor to the top edge of the book. Repeat and use the most repeatable value.
Model-specific sizing pages built from real geometry
Use these pages to rank bikes by stack, reach, and supported sizes before you open the calculator. Each guide links back into the tool with that frame preselected.
Choose by riding type
Compare race and endurance road geometry using stack, reach, bar drop, and cockpit length instead of relying on generic height charts.
Check how a gravel frame changes front-end height, reach, and stability before choosing between close sizes for long mixed-surface rides.
Use the calculator to understand how reach, stack, stem length, and off-road cockpit assumptions affect cross-country sizing decisions.
How to choose the right bike size
The fastest way to make a sizing mistake is to reduce the whole decision to rider height. Two bikes can both be sold as the correct size for the same rider while creating very different cockpit reach, bar drop, and saddle setbacks.
Use this tool to compare stack and reach first, then check what stem length, spacer stack, and saddle position each size needs to reach your target fit. If one size only works with extreme adjustments, it is usually not the cleanest choice.
That matters whether you are searching for a road bike size guide, a gravel bike fit calculator, or an MTB geometry comparison. The right frame is the one that gets you close to your target position before you start forcing the setup.
Bike fit FAQ
How should I use a bike fit calculator to pick a frame size?
Start with your body measurements, then compare how each frame size changes cockpit reach, bar drop, saddle position, and adjustment headroom. The best size is usually the one that reaches your target position with the fewest compromises.
What matters more for bike sizing: stack and reach or rider height?
Height is only a rough starting point. Stack and reach tell you how tall and how long the frame actually is, which makes them far more useful when two sizes are both technically within your height range.
Can I compare different bike models with this tool?
Yes. The TrainCraft bike fit tool includes model-specific geometry so you can compare different road, gravel, and MTB frames and see which one gets closer to your target setup.