To determine the appropriate bike size, you need to consider the rider's height and inseam. Here are some general guidelines:

For adult bikes, the height ranges are as follows:

• For a Small frame, the rider should be between 155-165 cm tall with an inseam of 72-78 cm [5).
• For a Medium frame, the rider should be between 165-175 cm tall with an inseam of 77-83 cm [5).
• For a Large frame, the rider should be between 175-183 cm tall with an inseam of 81-85 cm [5).
• For an Extra Large frame, the rider should be between 183-191 cm tall with an inseam of 86-90 cm [5).

For kids' bikes, the sizing is typically based on wheel size and the child's height:

• 12-inch bikes are for kids 28” – 38” tall [3).
• 14-inch bikes are for kids 36” – 40” tall [3).
• 16-inch bikes are for kids 38” – 48” tall [3).
• 18-inch bikes are for kids 42” – 52” tall [3).
• 20-inch bikes are for kids 48” – 60” tall [3).
• 24-inch bikes are for kids 56” – 66” tall [3).
• 26-inch bikes are for riders over 60” tall, regardless of age[3).