by Stan Purdum
Trying to figure out the correct bike size for yourself or maybe for a friend or for a kid’s bicycle? Here’s a chart to help you estimate which sized kids bike, road bike, hybrid bike or mountain bike you should probably ride.
The best way to figure out the right bicycle size is to try it out in person, at a local bike shop. But that isn’t always possible, and maybe you’re looking at a bike for sale on Ebay or somewhere else online.
A good bike shop can help you identify more than just if the frame size is correct. They can also help you figure out your optimal seat height and position, and whether or not the reach to the handlebars is optimal for comfort and bike control. Often, you can pay for a bike fitting at a good bike shop even if you didn’t buy the bicycle there, and it’s often worth the money to set up your bike fit optimally if you plan to spend more than an hour at a time riding the bike.
If you are actually spending money at a bike shop anyway, buying accessories like a helmet, tubes, a bike bag or apparel, it can be appropriate to ask for bike size guidance even if you don’t ultimately buy your bicycle at that shop. But to just go in to a bike shop and have someone help you figure out your bike size and to leave without ever intending to buy anything there is called “showrooming.” It is unfair to your local bike shop and wastes the time of paid employees.
Even experienced cyclists can find it hard to pick exactly the right size frame, because the geometry of a bicycle can vary depending on its design. The type of bike, your height and your riding style can also make a difference.
The most important body measurements for determining the correct bicycle frame size are your height and your inseam. While these two numbers alone will not guarantee that a bike is a perfect fit, by using them and a sizing chart, you can eliminate bikes that clearly are too tall or too short for you.
You no doubt already know your height, but the inseam measurement you need for bike sizing is not the same as the one you use when buying jeans, which will be at least two inches shorter than your actual inside leg length.
To find inseam length for cycle-fitting purposes, remove your shoes and any baggy trousers. Then stand with your feet about 8 inches apart and place a spirit level or other straight edge — even a book — in your crotch, pulling it up to the highest possible position, so that the pressure is similar to what you feel when sitting on a bike saddle. Keeping the straight edge parallel to the floor, measure the distance from the top of it to the floor. (It may be easier to have a helper do this.) For accuracy, repeat the measurement several times and calculate the average.
The inseam measurement will help you get a bike you can comfortably straddle, while the height measurement will help you get a one that will accommodate your upper body dimensions.
Next, using these charts below, determine which size bike will work for you.
Adult bicycle frames are normally measured from the middle of the bottom bracket to the top of the seat tube. Road bikes sizes are usually given in centimeters while mountain bike and hybrid sizes are usually given in inches. If you’re looking at a used bike online, you might need to contact the seller to provide this information, although they usually include it in the description. For hybrid sizing, see here.
Road Bike Size Chart
| Your Height / Inseam | Bike Size |
| 5′ to 5’4″ under 27″ inseam | XS (extra small) 49 cm bike |
| 5’4″ to 5’8″ with 27″ to 29″ inseam | S (small) 49 cm to 54 cm bike |
| 5’8″ to 5’10” with 29″ to 31″ inseam | M (medium) 52 cm to 56 cm bike |
| 5″10″ to 6′ with 31″ to 33″ inseam | L (large) 54 cm to 58 cm bike |
| 6′ to 6’3″ with 33″ to 35″ inseam | XL (extra large) 56 cm to 61 cm bike |
| 6’3″ to 6’6″ with 35″ and up inseam | XXL 61 cm bike or bigger |
We’ve charted road, mountain and kids bike sizes separately because each is measured differently because of their design and intended use. While there are several differences, hybrids, for example, are designed for more comfort than are road bikes, usually having a taller head tube and shorter top tube. Mountain bikes usually have a lower top tube than road bikes.
Mountain Bike Size Chart
| Your Height / Inseam | Bike Size |
| 5′ to 5’3″ under 27″ inseam | XS (extra small) 13 inch bike |
| 5’3″ to 5’7″ with 27″ to 29″ inseam | S (small) 15 inch bike |
| 5’7″ to 5’11” with 29″ to 31″ inseam | M (medium) 17 inch bike |
| 5’11” to 6’2″ with 31″ to 33″ inseam | L (large) 19 inch bike |
| 6’2″ to 6’4″ with 33″ to 35″ inseam | XL (extra large) 21 inch bike |
| 6’4″ to 6’6″ with 35″ and up inseam | XXL 23 inch or bigger |
Children’s bikes, as the chart shows, are sized according to the wheel size of the bike and the age of the child.
Kids’ Bike Size Chart
| Age | Wheel Size |
| 2 to 3 years | 12 inch |
| 3 to 5 years | 14 inch |
| 5 to 7 years | 16 inch |
| 5 to 8 years | 18 inch |
| 7 to 9 years | 20 inch |
| 9 to 12 years | 24 inch |
After you’ve narrowed your search by frame size, check to see whether the bike is for women or for men. While the two may look similar at a glance, those made specifically for women have geometry that better accommodates women’s usually shorter height and upper body dimensions. Thankfully, gone are the days when a “women’s” bike was a men’s bike painted pink.
For example, my adult daughter and I both have a similar inseam measurement, but she is 5’2″ and I am 5’7″. She can straddle my road bike, and it a pinch, ride it. But because her torso is shorter than mine, to do so very long forces her into an uncomfortable stretched out position. Her bike is from the extra small category while mine is from the medium category, but hers is also designed for a woman.
All of that said, the bike frame that works best for you is the one that fits your physiology. Thus, some women may be more comfortable on a “men’s” bike and vice versa. So if your body proportions fall outside of the norm, don’t assume you have to ride a bike that’s a poor fit. Any modern bike can be thought of as potentially “unisex.”
Once you have in your possession a bike that’s the correct frame size for you, the fit can be fine-tuned by adjusting saddle height and the fore-aft position of the saddle. If the reach to the handlebars is too near or too far, the stem can be switched out for a shorter or longer one. Even the crank arms and brake levers can be swapped for a difference size if necessary. The frame’s geometry is fixed, however, so you want to get that right at the start.
There are bike fit calculators online intended to help you get a bike with both the gross fit and the fine-tuning parts right, which can be helpful if you’re purchasing a new bike, but experienced riders who have tried such calculators say they sometimes miss the mark on some recommendations and are not as good as getting fitted by someone with bike fitting expertise.
Recommended Online Bicycle Fit Calculators
Here are two interactive bike fit calculators that we like that you could also try, in case you still aren’t sure after looking at our charts.
Competitive Cyclist https://www.competitivecyclist.com/Store/catalog/fitCalculatorBike.jsp#type
Pedal Force
http://pedalforce.com/online/bikefit.php
Did our guide help you choose the correct bike size?
Leave a comment and let us know how it helped, or comment with additional questions that you had that we can use to improve the guide.
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