Whether you ride on-road or off, pedal casually or competitively, it’s important to pay close attention to how your bicycle fits your body.  An ill-fitting bicycle can put excessive strain on low back, knees and even your neck. A properly fitted bike, however, will allow you to ride comfortably and safely, avoid injury, and produce more power, so you can go faster with the same or less effort. In general, when fitting a bicycle, there are five basic components to consider:

1. Frame size
2. Saddle (seat) height 
3. Saddle position
4. Saddle tilt 
5. Handlebar position

Frame Size 
Frame size is perhaps the most important of all measurements because once you purchase the bike, there are very few—if any—minor adjustments that can affect the overall frame.  Frame size is not necessarily dependent on your height; rather, it is more a matter of leg length. Simply, the frame should be easily straddled with both feet flat on the ground, and with perhaps an inch or two of clearance.

• For a road or hybrid bike, you should have an inch or two of clearance between your crotch and the top tube
• For a mountain bike, clearance should be about four inches—especially if you plan to ride in rugged terrain where an unplanned dismount is likely.

Note that frame sizes come in inches or centimeters, depending on the manufacturer. Also, a 21-inch frame from one company may fit very differently from the same size made by another manufacturer. Lastly, frame size is not the same as wheel size, which is commonly used in sizing kids’ bikes.

Saddle Height 
A saddle (seat) set too high or too low can cause pain and lead to injuries of the back and knees, and it will also affect the efficiency of each pedal stroke. As a starting point, set the saddle height so that your knee is slightly bent when the pedal is at its lowest position and the ball of your foot is on the pedal. It is recommended to make adjustments in very small increments and, if applicable, to wear your cycling shoes during the adjustment process.

Saddle Position 
To check the saddle position, sit on your bicycle, using a friend or a stationary object to keep yourself balanced, and rotate your pedals until they are horizontal (at the 3 o’clock and 9 o’clock positions). If your saddle is positioned properly, your forward knee should be directly over the respective pedal axle (with the ball of your foot on the pedal). For precise measurement, use a plumb-bob to help you visualize the alignment. If adjustments are needed, loosen the seat post and slide the seat saddle forward or backward, keeping the seat level. 

Saddle Tilt and Design 
Generally speaking, your saddle should be level. Check this adjustment by using a carpenter’s level balanced on the saddle while the bike is on level ground. If your saddle tips too much in either direction, pressure will be placed on your arms, shoulders and lower back.

Saddle selection is a matter of personal preference. Saddles come in gender-specific, comfort, and performance models. For example, women-specific saddles are wider at the back, have a shorter nose and usually have a soft or cut-out section in the middle.

Handlebar Position and Distance 
Handlebar setup is a matter of personal preference because it will affect shoulder, neck and back comfort. Generally, handlebars are positioned higher for comfort (a more upright riding position) and lower for improved aerodynamics.

Consult a Professional 
The above suggestions are general guidelines only. A quality bike shop should make the necessary adjustments for you or offer to help you fine-tune the fit of your bike, which is crucial to reduce wear and tear on the body, as well as minimize injuries. If there isn’t a bike pro at the shop you’re using, find one at another shop.

Always Wear a Helmet! 
A bicycle crash can happen at any time. However, according to the National Highway Safety Traffic Administration, a properly fitted bicycle helmet reduces the risk of head injury by as much as 85 percent and the risk of brain injury by as much as 88 percent. The following are tips to help ensure the correct helmet fit:

• The helmet should be level on the head, and it must cover the forehead.
• The Y of the side straps should meet just below the ear. 
• The chin strap should be snug against the chin so that when you open the mouth very wide, the helmet pulls down a little.
• Put your palm on the front of the helmet, and push up and back. If it moves more than an inch, more fitting is required. 
• Shake your head around. If the helmet dislodges, work on the strap adjustments.
• Do not wear a hat under the helmet.