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For my first bike, my dad took me to the local shop and had me make sure that I could stand over the bike without touching.
That was it.
We bought the bike and I rode the snot out of that single speed until long after I had outgrown it.
My second major bike purchase was a garage sale Cannondale that I bought with my paper route money. It was a small, purple women’s bike.
Once again, I put thousands of miles on this bike before someone suggested that I needed a bigger bike.
Growing up, bike sizing was a luxury we couldn’t afford.
(Road, Mountain and Hybrid sizing)
|< 5’0″||< 152 cm||XX-Small||47cm – 48cm||13″|
|5’0″-5’4″||152-163 cm||X-Small||49cm – 50cm||13-14″|
|5’4″-5’9″||163-175 cm||Small||51cm – 53cm||14-16″|
|5’10”-6’1″||178-186 cm||Medium||54cm – 57cm||16-18″|
|6’0″-6’4″||183-193 cm||Large||57cm – 60cm||19-21″|
|6’3″-6’8″||191-203 cm||X-Large||61cm +||23″|
Measure bikes from the center of the crank arm to the top of the seat tube.
Bike Sizing Theory
I’ll keep this section short. The principle you need to understand is that as the bike frame increases in height, it also increases in length.
For a long time, they would make the frames taller but would keep the top tube the same length. As bikes moved away from welded lugs, the bike manufacturers could start changing the top tube length with the height.
The end result is a much better fit.
However, keep in mind that on the top tube, we are mostly concerned with effective top tube length — that distance from the middle of the seat post to the middle of the headtube.
For most of our readers, effective top tube length won’t matter, but for the serious riders, it is something to watch for.
Just do an internet search for “bike model” + “geometry” and you should find a chart with all of the measurements.
The Dangers Of Getting The Wrong Size
I paid the price of wrong sizing. Because I trained so much on a smaller bike, I constantly have a difficult time finding a bicycle that doesn’t cause me pain.
My muscles developed in an incorrect manner so that when I finally get on a bike that is the correct size, my legs feel weak and powerless and I struggle with constant knee pain.
The trick for me is to push the saddle as far forward as I can. This helps me recreate the “hunched up” position that I used to ride, and lets me access all of my old muscle memory.
As it turns out, I got lucky. I can’t tell you how many 6-feet-tall people come into the shop complaining of neck pain. When they finally bring their bike in, they are riding a small bike like a bear on a trike.
Or you get those folks complaining of knee pain. It turned out they are still riding their dad’s 24″ frame (yes, I’ve seen that.).
Cycling is a unique sport in that it requires thousands of repetitive exercise motions. If you get the fit wrong, you can cause irreversible damage by forcing your body to contort into ways it simply should not.
And then, when you try to correct the situation, you sometimes have to undergo greater pain while your body stretches and relearns how to operate with the new configuration.
The Dangers Of Internet Sizing Charts
After years of fitting people for their bikes, I can pretty much size a person up as soon as they walk into the shop.
But preparing a sizing chart? That was a bit trickier.
I started with the bike manufacturer’s suggestions. Giant, Trek, and Specialized have great charts. And they mostly agree with each other.
And then I started looking at the other bike sizing charts out there.
It became pretty obvious that a lot of the blogs had just copied each other’s charts. I found one that was suggesting a 5’8″ person ride a large frame.
Yeah, that’s gonna cause problems.
Special Sizing Considerations
Manufacturer’s Custom Sizing
When is a “small” not a “small”?
When manufacturers get too creative. That’s when.
Anytime you can consult the manufacturer’s sizing chart, that will always be best.
However, most of the bike frames are made in a few overseas factories, and they pretty much follow similar conventions. So a generic chart like the one I have created tends to work pretty well.
The two major areas where I have seen manufacturers create custom sizing charts is for women’s specific models and triathlon bikes.
Weirdly enough, both of these bike frames have the same issue: a shorter top tube.
I’m not entirely sure why this throws the bike manufacturers off so much. But definitely, double-check their sizing recommendations if you have concerns.
Long Legs. Long Torsos.
Some of the online sizing charts try to offer an inseam measurement that you can use to help with your sizing. There are two problems with this:
1. Most people base their inseam measurement off of their pants’ sizing. For this, you need to measure your actual inseam from the groin to the ground.
2. There is no standardized methodology for sizing a bike based on inseam.
Long Legs? Size Up!
What you should be aware of is that longer legs in proportion to the rest of the body will often require you to get a taller bike with a shorter handlebar stem.
This is especially true for women. I’ve often sized long-legged women on the proper bike, but once we get them adjusted, their seat is several inches higher than their hands, causing excessive weight on their hands.
All that pressure on the hands inevitably leads to excessive numbness.
By going with a taller bike frame, I could help her get the correct height without stretching the saddle too high. Then, we replaced the handlebar stem with a shorter stem so she didn’t have to reach too far.
Short Legs? Size Down!
I’ve seen it go the other way in men. If you are all torso (like I am), then sometimes you need to size slightly down. I had a gentleman recently who should have been a medium (18″) frame.
We ended up sending him out on a small frame which allowed him to feel more in control. In this situation, I would have liked to add a longer stem to his bike, but he liked the setup we had.
This is much more rare in my experience. Since men have dominated the sport for so long, the sizing is pretty dialed for the dudes.
Professional Bike Fitting
The staff at your local bike store should be pretty solid on sizing. And most bike shops will put you on a trainer and take a minute to dial in your seat height, your seat forward and back position, and take some measurements on your elbow angles.
I have been in shops where a staff member had been in the industry for too long and refused to adjust their sizing technique. But that has become increasingly rare.
Most bike shop employees are very up to date with the best practices.
Is should be easy to arrange a local bike fit. Our shop does it for about $30, even for non-customers.
With more people buying bikes online, a local shop will often offer bike assembly, and a bike fits on the same day. Just call and work out the schedule with them.
Which Bike Fit Philosophy is The Best? (Retul vs. Dartfish vs. Trek vs. Serotta vs….)
The bike-fitting world is constantly evolving. Some of the methodologies are driven by a desire to provide a better fit.
Some of the methodologies are designed to keep from missing out on market share.
Retul is now one of the older methodologies out there but continues to be one of my favorite. The system images you while you ride, helping to correct fit problems that are not visible during a static fitting process.
The bottom line is, you need a good fitter. Read reviews. Get recommendations. Being able to draw from a decade of experience is invaluable when it comes to getting the ideal fit.