Frame size is the most important factor for comfort and control. It depends on type of bike, your height and leg length (inseam). The tables below are indicative — geometry differs from brand to brand.

Road bikes (approximate frame size):

• 47–49 cm — for 155–165 cm tall
• 50–52 cm — 165–172 cm
• 53–54 cm — 172–178 cm
• 55–56 cm — 178–185 cm
• 57–58 cm — 185–193 cm
• 60+ cm — over 193 cm

Mountain bike (indicative frame size):

• XS (13–14”) — 150–160 cm
• S (15–16”) — 160–170 cm
• M (17–18”) — 170–178 cm
• L (19–20”) — 178–185 cm
• XL (21–22”) — 185–193 cm
• XXL (23”+) — over 193 cm

Recommendations:

• Check the manufacturer's geometry sheet for that model — it's the most accurate source.
• Make sure you have space above the frame (standover) when standing over the bike.
• If you are between two sizes: for comfort and a relaxed position, choose the larger size; for maneuverability and a lower axle, choose the smallest.
• When possible, a test ride best clarifies the fit.

Information is indicative. For certainty, consult the manufacturer's size chart.