What size bike do you need (road and gravel): the ultimate practical guide
1) Measure yourself at home (quick and accurate)
You only need a wall, a large book, and a measuring tape.
- Height: barefoot, back against the wall, head neutrally aligned. Write down your height in centimeters.
- Inseam: press a book against your crotch (as if it were the saddle), measure from the top edge of the book to the floor. In centimeters.
- Torso (optional but useful): from the sternal notch (hollow between collarbones) to the edge of the book.
- Arm (optional): from the acromion (tip of the shoulder) to the center of your closed fist.
With height + inseam you can choose an initial size; with torso + arm you fine-tune stem length and reach.
2) Indicative initial size
Indicative table for road and gravel (adults). If in doubt between two sizes, choose the smaller one if you're looking for a sporty riding position; the larger one if you prioritize comfort.
| Height | Inseam | Road (letter) | Road (approx. cm) | Gravel (letter) |
|---|---|---|---|---|
| 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 | S/M | 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's usually a bit more stack (a higher position) than for road: if you're an M in road, you'll normally also be an M in gravel, but with a shorter stem and/or more spacers.
3) The real key: stack and reach
Stack = height of the head tube relative to the bottom bracket. Reach = horizontal distance from the bottom bracket to the center of the head tube. Together they define how high and long the frame positions you, regardless of traditional sizes or tubes.
Indicative ranges by style (frame + standard cockpit):
| Style | Stack/Reach (ratio) | Feel |
|---|---|---|
| Road Racing | ~1.40–1.50 | Aggressive, low, long |
| Road Endurance | ~1.55–1.65 | Comfortable, slightly higher |
| 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 standover (crotch–top tube clearance)
Compare your inseam with the standover height of the model and size:
- Road: comfortable clearance 2–4 cm.
- Gravel: 4–7 cm clearance (more room for technical maneuvers).
5) Fine-tune your position: saddle, cockpit, cranks
Saddle height (starting point)
Quick method: 0.885 × inseam (in mm) = center of bottom bracket to midpoint of the saddle. Adjust ±5 mm according to flexibility and feel. Check with your heel on the pedal (at 6 o'clock): knee extended without hip hunching.
Saddle setback
As a starting point, with the crank at 3 o'clock, the kneecap usually aligns with the pedal axle. This is not a hard rule: prioritize lumbar comfort and a feeling of power.
Stem and spacers
- Road: typical stem 90–120 mm. Longer = more stretched out and stable; shorter = more reactive.
- Gravel: 70–100 mm for technical control. Raise or lower stack by 5–10 mm with spacers to open or close chest/back.
Handlebars
- Road width: approximate to shoulder width (36–44 cm). If in doubt, equal to or 2 cm less than shoulders for a more aero position.
- Gravel: 2 cm wider than road or with flare (outward angle of drops) for control.
Cranks
- Height < 170 cm: 165–170 mm.
- 170–180 cm: 170–172.5 mm.
- > 180 cm: 172.5–175 mm.
Shorter cranks favor cadence and reduce hip flexion demands; longer cranks provide leverage but penalize cornering technique and technical gravel riding.
Unsure about your size? At Dog Days (Madrid), we'll fine-tune it with a professional bike fitting. Contact us via WhatsApp or check out our road bikes and gravel bikes.
