Bike Size Calculator
Find the ideal frame size for road, mountain, hybrid, gravel and kids’ bikes based on your height, inseam and riding style.
Bike size finder
Recommended bike size
Frame size
Fit details (approx.)
- Saddle height:
- Standover clearance:
- Suggested reach:
This is a starting point. Different brands and geometries can feel larger or smaller. When possible, compare reach and stack numbers or test ride.
Bike size charts (quick reference)
Road bike size chart (unisex)
| Height | Inseam | Frame size (cm) | Label |
|---|---|---|---|
| 150–160 cm | 68–74 cm | 47–50 | XS |
| 160–168 cm | 72–78 cm | 50–52 | S |
| 168–175 cm | 76–82 cm | 52–54 | M |
| 175–183 cm | 80–86 cm | 54–56 | L |
| 183–191 cm | 84–90 cm | 56–58 | XL |
| 191–198 cm | 88–94 cm | 58–61 | XXL |
Mountain bike size chart (hardtail / trail)
| Height | Frame size (in) | Label |
|---|---|---|
| 150–160 cm | 13–14" | XS |
| 160–168 cm | 15–16" | S |
| 168–178 cm | 17–18" | M |
| 178–185 cm | 18–19" | L |
| 185–193 cm | 20–21" | XL |
Kids’ bike wheel size chart
| Age (approx.) | Height | Wheel size |
|---|---|---|
| 2–3 yrs | 85–100 cm | 12" |
| 3–5 yrs | 95–110 cm | 14" |
| 4–6 yrs | 105–120 cm | 16" |
| 6–8 yrs | 115–130 cm | 20" |
| 8–11 yrs | 130–145 cm | 24" |
| 11+ yrs | 145+ cm | 26" / XS adult |
How this bike size calculator works
Bike sizing is mostly about matching your body proportions to the bike’s stack, reach and standover height. Because every brand uses slightly different geometry, this tool focuses on the fundamentals:
- Height gives a good first estimate of frame size.
- Inseam refines the result and helps with saddle height and standover.
- Bike type (road, MTB, hybrid, gravel, kids) changes the recommended formulas.
- Riding style adjusts the recommendation up or down for comfort vs. performance.
Formulas used
We use well-known fitting rules as a baseline and then apply corrections for bike type and riding style.
1. Saddle height (from bottom bracket to top of saddle)
We use the LeMond formula as a starting point:
Saddle height ≈ inseam × 0.883
This assumes clipless pedals and road position. For mountain or casual riding we shorten this slightly.
2. Road bike frame size (seat tube, center–top)
Common rule of thumb:
Frame size (cm) ≈ inseam × 0.65
If inseam is not provided, we estimate it from height using typical leg–torso proportions.
3. Mountain / hybrid frame size
MTB and hybrid frames are shorter and more upright, so we use:
- MTB size (in) ≈ inseam × 0.23
- Hybrid size (cm) ≈ inseam × 0.66
Riding style adjustments
Once we compute a “neutral” size, we adjust it slightly:
- Comfort / upright: we bias down about 1–2 cm (or ~0.5") for easier standover and shorter reach.
- Balanced: we keep the neutral size.
- Sporty / aggressive: we bias up about 1–2 cm (or ~0.5") for a longer, racier position.
How to measure your inseam correctly
- Stand barefoot with your back against a wall, feet 15–20 cm (6–8 in) apart.
- Place a hardback book between your legs, spine up, pushing it firmly into your crotch to mimic a saddle.
- Ask someone to measure from the floor to the top edge of the book.
- Record the value in centimeters or inches and enter it into the calculator.
Interpreting the results
Frame size
The calculator returns a primary frame size and, if you are between sizes, an alternative size. Use these as a range rather than a single “magic” number.
- Smaller size: more agile, easier standover, shorter reach.
- Larger size: more stable at speed, longer reach, potentially more efficient for flexible riders.
Saddle height
Saddle height is measured from the center of the bottom bracket to the top of the saddle along the seat tube line. It is a good starting point, but you should fine‑tune it:
- If your hips rock side to side when pedaling, lower the saddle slightly.
- If your knees feel cramped or you cannot fully extend your legs, raise it a few millimeters.
Reach and stack
Modern bike fit relies heavily on reach (horizontal distance from bottom bracket to top of head tube) and stack (vertical distance). Our calculator estimates a comfortable reach range based on your height and riding style, but you should compare this to the geometry chart of specific bikes.
Kids’ bike sizing tips
- Prioritize confidence and control over “growing into” a larger bike.
- On a first pedal bike, your child should be able to put the balls of both feet on the ground when seated.
- For balance bikes, a slightly smaller size that allows flat feet on the ground is ideal.
- Use both height and inseam to choose wheel size; age is only a rough guide.
Limitations and when to see a professional fitter
This calculator is designed to get you very close to the right size, but it cannot replace an in‑person fit if:
- You have a history of knee, back or neck issues.
- You are training or racing at a high level.
- Your proportions are very unusual (very long legs or torso).
In those cases, use this tool as a starting point and then work with a qualified bike fitter who can fine‑tune saddle setback, handlebar drop, cleat position and more.