BIKE SIZING
While most bikes can be adjusted to fit people within a range of different heights, it is safest and most efficient to ride a frame size that closest fits you. To find what size bike you are looking for, consider your height, or better yet, measure your inseam. When I say "inseam" I really mean it - run a tape measurer from your perinuem (the area between your butt and your sexy parts) down to the ground. The inseam is a better indicator than height, because people of the same height can have different inseam lengths, and the inseam is really what you worry about when standing over a bicycle. The chart below can be used to identify what size bike you should check out.
Road Bike Sizing
| HEIGHT (in) | INSEAM LENGTH (in) | BIKE SIZE (cm) |
|---|---|---|
| 4'10'' - 5'1'' | 25.5'' - 27'' | 46 - 48 |
| 5'0'' - 5'3'' | 26.5'' - 28'' | 48 - 50 |
| 5'2'' - 5'5'' | 27.5'' - 29'' | 50 - 52 |
| 5'4'' - 5'7'' | 28.5'' - 30'' | 52 - 54 |
| 5'6'' - 5'9'' | 29.5'' - 31'' | 54 - 56 |
| 5'8'' - 5'11'' | 30.5'' - 32'' | 56 - 58 |
| 5'10'' - 6'1'' | 31.5'' - 33'' | 58 - 60 |
| 6'0'' - 6'3'' | 32.5'' - 34'' | 60 - 62 |
| 6'2'' - 6'5'' | 34.5'' - 36'' | 62 - 64 |
Mountain Bike Sizing
| HEIGHT (in) | INSEAM LENGTH (in) | BIKE SIZE (in) |
|---|---|---|
| 4'11'' - 5'3'' | 25'' - 27'' | 13'' - 15'' |
| 5'3'' - 5'7'' | 27'' - 29'' | 15'' - 17'' |
| 5'7'' - 5'11'' | 29'' - 31'' | 17'' - 19'' |
| 5'11'' - 6'2'' | 31'' - 33'' | 19'' - 21'' |
| 6'2'' - 6'4'' | 33'' - 35'' | 21'' - 23'' |
| 6'4'' + | 35'' + | 23'' + |
Now that you’ve found the size you are looking for, it’s time to check out some bikes. The “size” of a bike frame is usually the distance from the center of the bottom bracket to the effective top of the seat tube. This is referred to as “c-t” measurement. To complicate this, other bike manufacturers indicate their bike sizes bike measuring from the center of the bottom bracket to the center of the top tube, called the “c-c” measurement. If you get confused, look at the diagrams below for measuring road and mountain bikes.
While a bike’s size is clearly more than this simple number, this is the best way of obtaining some sort of objective size measurement. Road bike frames are usually measured in centimeters (cm) while mountain bikes are measured in inches (in). Why measuring a bike is so complicated no mortal knows, and only the Ancient Bike Gods of Yore, in their infinite wisdom, can fathom why we must use these two obtuse systems. Noticing that no sizing system seems to work definitively, bicycle manufacturers have begun to simply measure their bikes in a small, medium, large, etc. system.
Road Bike Size Measurement
For road bikes with compact, or slanted, top tubes, the c-t or c-c measurement will be smaller than the bike's intended measurements. Pretend the bike has an imaginary top tube that is horizontal, and use this imaginary tube when finding the frame's c-t and c-c measurements. For example, a compact frame with a 47cm c-t measurement may actually fit like a 52cm frame and thus be labeled as a 52 cm bike.
Mountain Bike Size Measurement
There's gotta be an easier way!
If your puny brain is unable to deal with numbers and measurements, the most convenient method of bike fitting is simply to stand over the middle of the top tube. For a standard road bike with a horizontal top tube, shoot for about an inch of room between your perineum and the metal. For road bikes with compact geometry (a slanted top tube) that number can open up to about an inch and a half or maybe 2 inches. For mountain bikes, look for about 2 or 3 inches of room to keep your family jewels safe in case you experience a gravity-induced dismount.