Measure from the center of the steerer tube to the center of the handlebar clamp
Stem length is the distance from the middle of where the stem connects to your fork (the steerer tube) to the middle of where your handlebars clamp into the stem. This is the measurement that determines how stretched out or upright your riding position feels. You measure along the top of the stem, following the angle it sits at—not straight across.
Most stems range from 60 millimeters to 130 millimeters, with 90 to 100 millimeters being common on many bikes. Knowing your current stem length matters if you want to swap it for a different one, or if you are building a bike and need to match components that work together.
Key Takeaways
- Stem length runs from the center of the steerer tube (where it meets your fork) to the center of the handlebar clamp, measured along the stem's angle.
- You need a ruler or measuring tape marked in millimeters, and the measurement should be taken with the stem still on the bike or removed and laid flat.
- Most modern stems have the length printed on the side in small text, so check there first before measuring by hand.
- A longer stem pulls you forward and lowers your upper body; a shorter stem brings you more upright and closer to the wheel.
Gather a ruler or measuring tape marked in millimeters
You will need a tool that shows millimeters clearly. A standard ruler, a metal measuring tape, or a caliper all work. Avoid cloth measuring tapes because they stretch and give inaccurate readings. If you have a digital caliper, that is the most precise option, but a regular ruler is fine for this job.
Make sure whatever you use is long enough to span the stem—most stems are under 150 millimeters, so even a 12-inch ruler will cover it. Lay out your measuring tool on a flat surface or hold it steady against the stem so you can read the numbers without guessing.
Locate the center point of the steerer tube connection
The steerer tube is the fork part that slides up into your stem. On the stem itself, you will see a bolt or bolts on the front and back that clamp around this tube. The center point is the middle of that clamping area—imagine a line running through the middle of those bolts.
If your stem is still on the bike, look at where the stem meets the fork. If you have removed the stem, lay it on a flat surface with the steerer tube end facing you. Mark or identify the middle of that opening with your eye. This is your starting point for the measurement.
Measure along the top of the stem to the handlebar clamp center
Place your ruler or tape at the center point you just identified. Run it along the top surface of the stem—following the angle the stem sits at, not going straight across the bike. Stop at the handlebar clamp, which is the part that holds your handlebars. Find the center of that clamp (the middle of the bolts that squeeze the bars) and note where your ruler lands.
Read the number in millimeters. That is your stem length. Write it down so you do not forget it. If the number falls between two millimeter marks, round to the nearest whole number.
Check the stem itself for a printed measurement
Before you measure by hand, flip the stem over or look at its sides. Most modern stems have the length stamped or printed directly on the aluminum or carbon in small text. You might see something like "90mm" or "100 x 31.8" (the second number is the handlebar clamp diameter, which is separate). This printed number saves you the trouble of measuring.
If the print is worn away or your stem is older, the hand measurement method will give you an accurate reading. Some vintage stems may not have been marked at all, so measuring is your only option.
Common mistakes to avoid when measuring
Do not measure from the very bottom of the steerer tube opening to the very end of the handlebar clamp—that gives you a longer number than the actual stem length. The measurement starts at the center of the steerer tube connection, not the edge.
Do not measure straight across the bike if your stem is angled upward or downward. Follow the stem's actual angle from top to bottom. If you measure straight across, you will get a number that is too short. Also, make sure your ruler is not bent or twisted as you take the measurement—keep it flat and aligned with the stem's centerline.
If your stem has a rise (an upward angle built into it), the measurement still runs along the top surface, not at a right angle to the bike frame. The stem's angle is part of its design, and your measurement should follow that angle.
Frequently Asked Questions
What is the difference between stem length and reach?
Stem length is the single measurement from steerer tube center to handlebar clamp center. Reach is a different spec that some manufacturers use to describe how far forward the handlebars sit relative to the fork. Reach is less common and varies by brand. Stick with stem length for ordering replacement stems.
Does stem length affect how my bike handles?
Yes. A longer stem (110mm or more) stretches you forward and lowers your body, which can feel more aggressive. A shorter stem (80mm or less) brings you more upright and closer to the front wheel, which feels more responsive but less stretched. Changing stem length changes your riding position and how the bike feels in turns.
Can I measure the stem while it is still attached to the bike?
Yes, you can measure it on the bike. It is often easier to remove the stem first and lay it flat on a table, but measuring it in place works if you can hold your ruler steady and see the center points clearly. Removing it takes only a few minutes and gives you a clearer view.
What if my measurement does not match any standard stem size?
Stems come in 10-millimeter increments: 70mm, 80mm, 90mm, 100mm, 110mm, and so on. If your measurement is 95mm, you have a 90mm or 100mm stem—check the printed marking on the stem to see which one it actually is. Manufacturers sometimes round the printed size, or your measurement may be slightly off due to how you held the ruler.
Do I need to know my stem length to buy a new one?
Yes. When you order a replacement stem, you need to specify the length, the steerer tube diameter (usually 1 1/8 inch on modern bikes), and the handlebar clamp diameter (usually 31.8mm). Knowing your current stem length helps you decide if you want the same size or a different one based on how your bike feels.