Measure spoke length from the inside of the nipple to the center of the hub hole
A spoke runs from a hole drilled in your wheel hub to a hole drilled in your rim. To get the right replacement length, you measure from the inside of the nipple (the threaded piece that sits on the rim) to the center of the hole in the hub where the spoke seats. This is the only measurement that matters—not the total length of the spoke, not the length of the thread, just the distance between those two points.
The reason this matters is that spokes come in half-millimeter increments, and being off by even 2 or 3 millimeters can mean the spoke either bottoms out in the hub hole (and won't tighten properly) or doesn't reach the nipple at all. Getting the length right is what lets you true the wheel and keep it true.
Key Takeaways
- Spoke length is measured from the inside of the nipple to the center of the hub hole, not from end to end.
- You can measure an existing spoke with a ruler or caliper, or calculate the length using your hub diameter, rim diameter, and spoke count.
- If you do not have a working spoke to measure, you will need to know your hub flange diameter, rim diameter, and how many spokes your wheel has.
- Spokes are sold in half-millimeter increments, so rounding to the nearest half-millimeter is normal.
- If you are unsure of your measurement, a bike shop can measure your wheel and sell you the correct length.
Measuring an existing spoke with a ruler or caliper
The simplest method is to remove a spoke from your wheel and measure it directly. Unscrew the nipple at the rim end, then pull the spoke out. Lay it on a flat surface with a ruler or digital caliper.
Place the zero end of the ruler or caliper at the inside edge of the nipple (the end that was threaded into the rim). Measure to the center of the hole at the hub end—the point where the spoke was seated in the hub. Write down the measurement in millimeters. If you get 293 mm, for example, that is your spoke length.
If you do not have a caliper, a ruler works fine, though a caliper is more accurate. If the measurement falls between two half-millimeter marks (say, between 293 and 293.5), round down to the lower half-millimeter. Spokes are always sold in half-millimeter increments: 290, 290.5, 291, 291.5, and so on.
Calculating spoke length if you cannot measure an existing spoke
If your wheel is too damaged to safely remove a spoke, or if you are building a new wheel, you can calculate the length using three measurements: the hub flange diameter, the rim diameter, and the number of spokes.
The hub flange diameter is the distance across the circle formed by the spoke holes in the hub. Measure from the center of one spoke hole, across the center of the hub, to the center of the spoke hole directly opposite. The rim diameter is the distance across the rim from edge to edge, measured through the center. Count the number of spokes in your wheel.
With those three numbers, you can use an online spoke calculator (search "bicycle spoke length calculator") to get the exact length. You enter the hub flange diameter, rim diameter, and spoke count, and the calculator returns the length in millimeters. This method is accurate as long as your measurements are precise.
Why spoke length varies between wheels
Two wheels that look the same size can need different spoke lengths because the hub flange diameter varies. A road bike hub and a mountain bike hub may have different flange diameters even though both wheels are 700c or 26 inches. A rear wheel hub is often wider than a front wheel hub on the same bike, which changes the spoke length.
Rim width also affects spoke length slightly. A wider rim moves the spoke holes farther from the center, which changes the angle and length of each spoke. This is why you cannot assume two wheels are the same just because they are the same nominal size.
What to do if you measure two different lengths
If you remove spokes from different positions on the wheel and get different measurements, your wheel may be hand-built or may have been repaired with mismatched spokes. This is uncommon but happens. Measure at least three spokes from different positions around the wheel. If they are all the same length (within 1 mm), use that length. If they differ, measure the spokes on the side of the wheel you are repairing and use the most common length you find.
If you are replacing all the spokes in a wheel, consistency matters more than matching the old spokes exactly. A wheel built with all spokes of the same length will be easier to true and will stay true longer than one with mixed lengths.
Measuring for a wheel you do not own
If you are ordering spokes for someone else's bike and cannot measure the wheel directly, ask them for the hub model and rim model, or ask them to measure the hub flange diameter and rim diameter themselves. A photo of the wheel with a ruler next to it can also help. If they cannot provide those details, a bike shop can measure the wheel in person and order the correct spokes.
Do not guess based on wheel size alone. A 700c road wheel and a 700c gravel wheel may need different spoke lengths because the hubs are different.
Frequently Asked Questions
Can I use spokes from a different wheel if they are the same size?
Not safely. Wheel size (like 700c or 26 inches) does not tell you spoke length. The hub flange diameter and rim diameter determine the length. Two 700c wheels can need spokes that differ by 5 mm or more. Always measure or calculate the length for the specific wheel you are building.
What if I order spokes that are 2 mm too long?
The spoke will not seat properly in the hub hole and will not tighten fully. The nipple may strip or the spoke may bend. Order the correct length. If you have already ordered the wrong length, a bike shop can help you return them or may have the correct length in stock.
Do I need to measure both sides of a rear wheel?
Yes. The drive side (right side) and non-drive side (left side) of a rear wheel often have different spoke lengths because the hub flanges are at different distances from the center. Measure or calculate the length for each side separately.
Can a caliper measure spokes accurately enough?
Yes. A digital caliper is actually better than a ruler for this job because it reads to the nearest millimeter and is easier to position at the nipple and hub hole. A ruler works too, but a caliper is faster and more precise.