What size bike do you need (road and gravel): the ultimate practical guide
1) Measure yourself at home (quickly and accurately)
All you need is a wall, a large book, and a meter stick.
- Height : barefoot, back against the wall, head neutrally aligned. Note your height in centimeters.
- Inseam : Press a book against your pubic bone (as if it were a saddle), and measure from the top edge of the book to the floor. In centimeters.
- Torso (optional but useful): from the sternal notch (dimple between collarbones) to the edge of the book.
- Arm (optional): from acromion (shoulder point) to the center of the closed fist.
With height + inseam you can choose a starting size; with torso + arm you fine-tune power and reach.
2) Initial indicative size
Guideline table for road and gravel bikes (adults). If you're unsure between two, choose the smaller one if you're looking for a sporty riding position; the larger one if comfort is your priority.
| Height | Crotch | Road (letter) | Road (approx. cm) | Gravel (lyrics) |
|---|---|---|---|---|
| 155–165 cm | 70–76 cm | XS | 47–50 | XS |
| 165–170 cm | 74–80 cm | S | 51–53 | S |
| 170–175 cm | 77–83 cm | YE | 53–54 | M |
| 175–180 cm | 80–86 cm | M | 54–56 | M |
| 180–185 cm | 83–89 cm | L | 56–58 | L |
| 185–190 cm | 86–92 cm | XL | 58–60 | L/XL |
| 190–195 cm | 90–96 cm | XL/XXL | 60–62 | XL |
For gravel there is usually a bit more stack (higher position) than on road: if on road you are M, on gravel you are usually also, but with less power and/or more spacers.
3) The real key: stack and reach
Stack = height of the head tube relative to the bottom bracket. Reach = horizontal reach from the bottom bracket to the center of the head tube. Together they define how tall and long the frame makes you, regardless of "traditional" sizes or tube sizes.
Indicative ranges by style (frame + standard cockpit) :
| Style | Stack/Reach (ratio) | Sensation |
|---|---|---|
| Road Racing | ~1.40–1.50 | Aggressive, low, long |
| Endurance Road | ~1.55–1.65 | Comfortable, slightly taller |
| Gravel Race | ~1.55–1.65 | Fast, stable |
| Gravel Adventure | ~1.65–1.75 | Very comfortable, technical control |
If you have a bike that fits you perfectly, check its stack/reach and look for equivalents in the new bike (Aurum, Orbea, Factor, Basso) to get it right the first time.
4) Check the standover (clearance between crotch and tube)
Compare your inseam to the standover height of the model and size:
- Road : comfortable clearance 2–4 cm.
- Gravel : clearance 4–7 cm (more margin for technical maneuvers).
5) Fine-tune the position: saddle, cockpit, cranks
Saddle height (starting point)
Quick method: 0.885 × inseam (in mm) = center of bottom bracket to midpoint of saddle. Adjust ±5 mm according to flexibility and feel. Check with heel on the pedal (at 6 o'clock): knee extended without hip contraction.
Saddle setback
As a starting point, with the crank arm at 3 o'clock, the kneecap is usually close to the pedal axle. This isn't a hard and fast rule: prioritize lumbar comfort and the feeling of power.
Power and spacers
- Road bike : typical stem length 90–120 mm. Longer = more extended and stable; shorter = more responsive.
- Gravel : 70–100 mm for technical control. Raise or lower the stack by 5–10 mm with spacers to open or close the chest/back.
Handlebar
- Road width : approximately shoulder width (36–44 cm). If in doubt, choose the same or 2 cm less than shoulder width for a more aerodynamic posture.
- Gravel : 2 cm wider than road or flare (opening in falls) for control.
Connecting rods
- Height < 170 cm: 165–170 mm.
- 170–180 cm: 170–172.5 mm.
- > 180 cm: 172.5–175 mm.
Shorter wheels improve cadence and reduce hip flexion requirements; longer wheels provide leverage but penalize cornering technique and gravel riding technique.
