Bike Frame Size Calculator

How to calculate Bike Size calculator?

This calculator estimates a recommended frame size from your inseam measurement and a small bike-type adjustment to better match riding position.

Key formula: ideal_frame_size_cm = inseam_cm * 0.67 + sizing_factor

Using the Bike Size calculator calculator: an example

Example values used below: inseam = 78 cm, preferred bike type = Mountain Bike.

Step-by-step calculation:

1. Start with inseam: 78 cm → base size = 78 × 0.67 = 52.26 cm.
2. Apply bike-type adjustment (Mountain Bike +2 cm): 52.26 + 2 = 54.26 cm.
3. Round to the nearest whole number: recommend a 54 cm frame.
4. Confirm with a test ride and fine-tune by 1 to 2 cm for comfort and riding style.

Frequently Asked Questions

Can I use overall height instead of inseam?

Height gives a rough estimate but inseam is more accurate for frame sizing because it reflects leg length and standover requirements.

How do bike types affect sizing?

Different bike types use slightly different geometry; the calculator adds a small sizing_factor to account for more relaxed or aggressive riding positions.

Should I round up or down when choosing a frame?

Round to the nearest whole number as a starting point; if between sizes, consider intended fit (race fit → round down, comfort fit → round up) and test ride when possible.