Bike geometry, side by side
Find the frame that actually fits.
Stack, reach, angles and trail from official manufacturer geometry charts. Compare up to four bikes — and see exactly what changes at the bars and the saddle.
The comparison
Start here
Add a bike you already know fits.
Pick a brand, model and size. Then add a second frame to see the difference — in numbers, in profile, and at your contact points.
Road, gravel and mountain · no account · no tracking
01
Profile
Overlaid at the bottom bracket. Wheel circles use nominal diameters.
02
The numbers
All dimensions in millimetres unless marked. Deltas are against bike A; “—” means the figure was not published.
03
What changes
Bar positions assume a 100 mm / −6° stem and 30 mm of spacers.
04
Similar fits
Every published size close to bike A's stack and reach, ranked by how close it sits. One size per model.
Fit transfer
Keep the position.
Change the frame.
Stack and reach describe the frame. Your stem, spacers and saddle height turn that into a fit. Here is what carries over — and what you need to change.
No bikes to compare yet.
Add a bike on the compare screen, then come back. Your reference bike supplies the position to copy.
01
Your reference setup
Saved in this browser.
Saddle height is measured along the seat tube, centre of BB to top of saddle. Spacers include the headset cover; the calculation adds 20 mm for the stem clamp.
02
What it takes
Same stem angle, same saddle height.
Bar X is measured forward from the bottom bracket; Bar Y upward. Setback is measured behind the BB. Deltas compare each bike with the reference at the same saddle height.
The assumptions
- Bar clamp X/Y is the centre of the stem's handlebar clamp, measured from the bottom bracket. Handlebar reach, drop and hood position are not included.
- A −6° stem on a 73° head tube rises 11° above horizontal; a 17° stem on the same head tube is level. The solver keeps your stem angle and solves for length and spacers.
- Spacer changes are measured along the steerer. Raising the bar by 10 mm needs roughly 11 mm of extra spacer at a 65° head angle.
- Saddle setback follows the effective seat angle at your saddle height. Two bikes with the same saddle height but different seat angles put the saddle in different places.
Data & method
Numbers you can
argue with.
Where the geometry comes from, how the derived figures are calculated, and what this site deliberately does not do.
Source
Every geometry row is imported directly from an official manufacturer geometry page or PDF. Current coverage is the full current Trek and Giant ranges plus a flagship model from 18 other major brands. Every size keeps a link to its source page; no third-party geometry aggregator is used.
This is a curated database, not a live feed. Models and running changes are added as they are imported. Check the manufacturer's chart before you buy.
Rows are tagged manufacturer; a model year is marked verified only after every published value has been checked by hand. The count of hand-verified sizes is shown at the bottom of this page.
Derived figures
- Stack / Reach
- Stack divided by reach. Lower is longer and lower; higher is shorter and taller. Useful for comparing the front-end shape across sizes.
- Trail est.
- When the source publishes trail, that figure is shown. Otherwise trail is estimated as
(R·cos θ − rake) / sin θ, where R is the nominal wheel radius and θ is the head angle. Tyre assumptions: 700×28 road, 700×40 gravel, 29×2.4 and 27.5×2.4 mountain. Trail moves with tyre size, so treat estimates as a comparison tool, not a spec. - Front centre
- Wheelbase minus chainstay when both are published. Otherwise the steering-axis construction is used. Small differences from the manufacturer's figure are normal because chainstay length is measured along the tube.
- Bar clamp
- Reach − h·cos θ + stem·cos(90° − θ − stem angle), with the vertical equivalent for height, where h is spacers plus 20 mm of headset and stem clamp. This is the stem's bar clamp, not the hoods.
- Saddle setback
- Saddle height × cos(effective seat angle), measured behind the bottom bracket. It assumes the saddle sits directly above the seat tube.
Known limits
- Blank cells mean the source did not publish a figure, or the value failed a sanity check. They are never filled with a guess. The one exception is the drawing, which falls back to a 70 mm (road/gravel) or 30 mm (MTB) BB drop when none is published.
- “Effective” seat angle is used throughout; actual seat tube angle can differ on curved or interrupted seat tubes.
- Suspension bikes are compared at their published static geometry. Sag changes angles, stack and BB height out on the trail.
- Frame size labels are not standardised. A 54 from one brand is not a 54 from another — compare the numbers, not the sticker.
- This site is independent and unaffiliated with any brand. No cookies, no accounts, no tracking scripts.
Dataset build — · — sizes · — e-bike sizes · 0 verified by hand