Bike Size Calculator

Your height provides a starting point, but inseam measurement determines the best frame size. Generally, riders 5'6"-5'9" need 52-55 cm road bikes or 17-18" mountain bikes. Measure your inseam by standing against a wall with a book pressed between your legs, then measure from floor to book top. Compare both measurements to manufacturer size charts for the most accurate recommendation. Remember that body proportions vary—someone with longer legs relative to their torso may need a different size than height alone suggests.

Calculate frame size by multiplying your inseam measurement (in centimeters) by 0.67 for road bikes or 0.66 for mountain bikes. For example, an 84 cm inseam × 0.67 = 56 cm road frame. This formula gives you a baseline, which you should verify against specific manufacturer charts. Different brands interpret measurements differently, so the calculated number serves as a starting point rather than an absolute answer. Test riding whenever possible confirms whether the calculated size feels right.

A 26-inch wheel bike typically fits riders 4'10"-5'7" tall (147-170 cm). The 26-inch measurement refers to wheel diameter, not frame size. These bikes come in various frame sizes—usually 13"-18" for adults or XS-M sizing. Check the specific frame dimensions and standover height for your measurements. Children's 26-inch bikes work for ages 11+ or kids around 4'5"-5'0" tall. Frame size matters more than wheel size for proper fit, so prioritize finding the right frame measurements for your body.

The choice between 28-inch (700c) and 29-inch wheels depends on bike type and your height. Road bikes use 700c wheels (roughly 28 inches), suitable for riders 5'0" and taller across various frame sizes. Mountain bikes with 29-inch wheels work best for riders 5'7" and taller, offering better rollover capability on rough terrain. Shorter riders (under 5'6") often find 27.5-inch mountain bike wheels more manageable. The wheel size affects handling and fit, so consider your riding style—29ers provide stability and speed, while smaller wheels offer quicker handling.

Riding a bike that's too small creates several problems but is generally safer than riding one too large. A small frame causes cramped positioning, leading to knee pain, back strain, and reduced power output. You'll notice difficulty extending your legs fully while pedaling and an uncomfortably hunched posture. However, you'll maintain better control and can easily put your feet down when stopping. If you must choose between sizes, slightly too small beats too large for casual riding. For serious cyclists or long distances, improper sizing of any kind causes enough discomfort and efficiency loss to warrant getting the right size.

Measure from the center of the bottom bracket (where the pedals attach) to the top of the seat tube (where the seatpost enters the frame). Road bikes measure along the seat tube, while mountain bikes sometimes measure to the center of the top tube. Use a tape measure or ruler, recording the measurement in centimeters for road bikes or inches for mountain bikes. This measurement gives you the frame's official size. For accurate comparison with manufacturer specs, also measure the top tube length (horizontal distance from head tube to seat tube) and standover height (ground to top tube at the point where you'd stand over the bike).

Frame size measures the bicycle's frame from bottom bracket to seat tube (like 54 cm or 17"), determining how the bike fits your body. Wheel size measures the diameter of the wheels (like 26", 27.5", or 29"), affecting ride quality and handling. You need both measurements to be appropriate for your height. A 26-inch wheel bike comes in multiple frame sizes—the wheel size doesn't tell you if the frame fits. Taller riders typically need both larger frames and larger wheels, while shorter riders use smaller frames, though wheel size depends more on bike type and preference.

Yes, but kids' bikes follow different sizing rules. Children's bikes are sized primarily by wheel diameter (12", 16", 20", 24") rather than frame measurements. Match wheel size to the child's age and height: 12" for ages 2-4, 16" for ages 4-6, 20" for ages 6-8, and 24" for ages 8-12. The most reliable method is checking standover height—the child should stand over the bike with both feet flat on the ground and have 1-2 inches of clearance. Kids grow quickly, so many parents choose the larger size if the child is between sizes, but proper standover clearance is non-negotiable for safety.

No, sizing varies significantly between brands. A size 54 from one manufacturer might fit like a 52 or 56 from another brand. European brands often run smaller than American brands. Mountain bike sizing particularly varies, with some brands using S/M/L categories while others use inches, and the actual measurements behind these labels differ. Always check the specific brand's geometry chart, which shows actual frame measurements like top tube length, seat tube length, and standover height. These numbers provide reliable comparison points across brands. Test riding different brands in your size range reveals these differences clearly.

Road bikes need 1-2 inches (2.5-5 cm) of clearance between your crotch and the top tube when standing over the bike. Mountain bikes require 2-4 inches (5-10 cm) due to rougher terrain where you might need to bail off quickly. Measure standover by straddling the bike in your regular shoes while standing flat-footed. If the frame touches you or comes within half an inch, it's too large. Bikes with sloping top tubes provide more clearance, allowing riders at the upper end of a size range to fit comfortably. This clearance isn't just for comfort—it's a safety requirement for emergency stops and dismounts.