The stem on your bike (the part that connects your handlebars to the rest of the bike) can make a significant difference in your bike’s performance and your comfort on the bike. After all, the length of the stem can drastically change how much leverage you have while you’re steering. Find out how to measure bike stem length accurately with us.
The length and rise of your bike stem can also make a big difference in how comfortable you are and how much arm fatigue you get while riding.
After all, handlebars that are too close can put extra stress on your elbows and shoulders, while handlebars that are too low force you to lean forward into a more aggressive rider position.
Fortunately, measuring the stem on your bike isn’t too difficult. We’ll cover how to measure the stem length on a road bike and a mountain bike, along with everything else you need to know to choose a new bike stem if you need to change the length or height on your bike.
Basic Bike Stem Measurement Info
Before we get started on how to measure a bike stem length of your stem (and all its other dimensions as well), you’ll need to know a little more about your stem.
Bike stem sizes are measured in millimetres. The sizes are 10 mm different, from 70mm to 140mm. Since the stem length is measured in millimetres, it’s especially important to make sure you’re measuring carefully since a small mismeasurement might put you in a different size.
If your measurement doesn’t come up to a multiple of ten, round your measurement to the nearest number ending in 0. Chances are you just made a slight measurement error. It’s a good idea to double-check your measurement to be sure though.
The other thing to remember is that the length of your stem might be slightly misleading if you have a rise in your stem (we’ll talk about measuring the rise in your stem later). If the stem of your bike has a rise, the length of your stem will be longer than its reach.
Stem reach is the horizontal distance between the attachment to your bike frame and the connection to your handlebars. If the bike stem has a rise you’ll need to know both the rise (the vertical distance) and the reach (the horizontal distance) covered by your stem.
That way, when you pick a new stem, you can keep the same rise with a different length, change both dimensions, and get a shorter stem or larger rise with the same length. It’s all a matter of what you need from your bike stem.
How to Measure Road Bike Stem Length
Road bikes are likely to have a mostly horizontal stem with little or no rise since they tend to have more aggressive rider positions than other styles of bike. That means that you’re less likely to need to calculate the rise on a road bike stem. You may still want to consider road bikes with a rise though if you’ve noticed arm fatigue or want to sit a tiny bit more upright position in the saddle.
To measure the stem length of road bikes, you first need to mark the centre point where the stem attaches to the bike frame and the centre point where it attaches to your handlebars. The length between the two parts is always shorter than your true stem lengths.
Just measuring from connection point to connection point will almost always lead to buying a shorter stem. That’s why it’s important to mark those centre points, so you get the right measurement.
Lean your bike up against a wall or stabilize it with a bike rack or frame. It doesn’t matter what you use so long as the bike is stable enough for you to measure, without twisting the handlebars. Twisting won’t change the length of your stem, but it can make it more difficult to get an accurate measurement.
Now, take a tape measure with centimetre and millimetre markings in addition to inch marking. Measure from the two centre points you identified earlier, in either millimetres or centimetres.
A centimetre is 10 millimetres, so you can do some simple math to get your stem size.
If your bike does have some rise, you’ll want to measure that separately. We’ll cover it in a moment.
How to Measure Mountain Bike Stem Length
You’ll use the same basic steps to measure the length of your mountain bike stem that we outlined for measuring road bike stems. That is:
- Mark the centre point where the stem connects to the bike frame and where it connects to your handlebar.
- Measure between the two centre points with a tape measure with centimetre and millimetre markings.
- Round your measurement to the closest centimetre to determine the size of your current stem.
However, you’re a lot more likely to be dealing with a rise on mountain bike stems or gravel bike stems.
If your bike stem has a rise (your handlebars are slightly higher than the connection to your bike frame), you’ll want to get two other measurements in addition to the length of your stem. You’ll want to measure the rise, which we’ll cover in a moment, and the reach.
To get the reach of mountain bikes, you’re only going to measure the horizontal distance between your handlebars and where your stem meets the bike frame. You can either use paper to draw the distance, or you can use a ruler and measure from the handlebars to the frame connection of mountain bikes without following the stem angles.
That would mean that your ruler is sticking out unsupported though, and you’ll have to eyeball the measurement. If you have a level with centimetre measurements, that might be the best tool because you’ll be able to tell when it’s completely horizontal for the most accurate reach.
Length is a combination of reach and rise, so knowing your reach will help you make the exact adjustment you need in mountain bikes, without changing your stem in other dimensions.
How to Measure Stem Width
The majority of modern bike stems are going to use a 1 1/8″ stem width, but some older bikes will still have one-inch connections instead of 1 1/8″. There are connectors to help adapt bike stems and frames of different widths, though. While you need to know your stem width, there are usually plenty of adaptor options.
To measure the width, just measure with the tape measure perpendicular to the stem. Since the width is measured in inches and fractions of an inch, you’ll use that part of the tape measure. Unfortunately, since the width measurements are fairly precise, there isn’t any rounding for this measurement.
How to Measure Stem Rise?
Rise isn’t measured in the inches you get in the lift, which is a combination of the rise and the reach. Instead, it’s measured in the degrees of lift in the stem.
The best way to measure the rise of your stem is with a protractor. Line up the protractor so that the vertical line of the stem attachment is at the centre. Then use a pencil or another straight tool as a straightedge to match the stem angle.
The degrees above 0 are the rise of your stem. So it might be a 6 or 7-degree rise, or 0, or any measurement in between.
You might also see stem rise listed as the degree of the rise + 90. That’s because if you turn the protractor on its side, to that 0 degrees is vertical instead of horizontal, the rise will be between 90 degrees (0) or 100 degrees (10) on most bikes.
What Do You Need to Know About Handlebar Width?
For most cyclists, your handlebar will be most comfortable if it’s about the same width as your shoulders. Specifically, the distance between the two joints.
To find that width, you’ll need to find the bump on the top of your shoulder. That’s joint. Measure between the bumps to find the right width for your handlebars.
However, some cyclists prefer their handlebars to be a little wider than their shoulders. That can be more comfortable for some riders, and can also make steering a little easier since wider handlebars are more aggressive overall.
How to Measure Handlebar Diameter?
There are two easy ways to measure handlebar clamp diameter (you can also use these methods for your stem length if you prefer), callipers, or wrapping a measuring tape around the center of the handlebar.
Callipers are the easier of the two since you just need to adjust them until you have the right measurement, and you’re done.
But, if you don’t have callipers, you can measure around the handlebar. Divide the measurement by pi (3.14), and you have your standard diameters.
What About Handlebar Clamp Design?
The vast majority of stem clamps use a sturdier 4 bolt design for the front bar clamp. It’s just sturdier and more durable overall.
For the rear clamp on your stem, there is a little more variation, including both 2-bolt and 4-bolt designs. A few rarer handlebar clamp designs will use a wedge design with a single bolt for the attachment with the bike frame/fork steerer tube.
That’s it, that’s everything you need to know to get an accurate measurement of your bike stem, and how to choose a new stem design to make some slight adjustments.
There are tons of great bike stems out there, but if you’re looking for something different, here are some of the best. The Wake Mountain Bike Stem Short Handlebar Stem is a good option if you’re looking to put your handlebars right on top of your fork steerer tube and don’t need any added reach or rise to make your bike comfortable.
For a slightly longer and more adjustable stem, we recommend the FOMTOR Adjustable Stem 0~90 Degree, which will allow you to customize the stem a little differently every day.
Or, for a little bit of a rise and some added reach, the FOMTOR 31.8 Stem 35 Degree 70mm 90mm 110mm Bike Handlebar Stem Riser comes in several convenient sizes, which makes it easy to find a good fit.