Spoke Length Calculator

On this page you can calculate the needed length of bicycle spokes.

Rim type: 
Hub type: 

left
right
Effective rim diameter:  mm
Hole circle diameter of hub flange:  mm   mm
Distance hub flange to wheel center line:  mm   mm
Number of spokes: 
Number of spoke crossings:

Explanation

In case you don’t need different values for the left and for the right side, just leave the “right” side empty – the values will automatically be used from the “left” side.

If your rim or hub type is already in the database, you may use the values from there – select an entry and click on “Use values”. Complete the missing values as needed and then click on “Calculate” to get the results.

You can also just enter the values for the number of spokes and spoke crossings, select a hub and rim type and directly click on “Calculate”.

Effective rim diameter: This is the inner diameter of the rim, measured from the point, where the heads of the spoke nipples bear on the rim well. If you manually measure the rim, you should add about 3 mm to the measured diameter. If you have the exact technical data of the rim, you should enter the “effective rim diameter”, in short “ERD”.

Hole circle diameter of hub flange: This is the diameter of the circle, where the spoke holes in the hub are. If you use a hub for disc brakes, you may have different diameters on each side.

Hub, hole circle diameter of flange

Distance hub flange to wheel center line: This is the distance from the center line of one hub flange to the center line of the wheel.

For symmetric hubs this is exactly half of the distance from one flange center line to the other.

For asymmetric hubs (freewheel hubs, hubs for disc brakes), the rims are not centered but offset a bit against the hub – therefore you have to use spokes with different lengths on each side and you have to enter the according values for “left” and “right”.

Hub, flange distance

Number of spokes: Here you have to enter the whole number of spokes for the wheel, e.g. 32, if the hub has 16 spoke holes on each side.

Number of spoke crossings: Enter 0, if you want to build the wheel (or one side of the wheel) with radial spokes.

Formula

The calculation is done using the following formula for each side:

spokecalc-formula

D – effective rim diameter
d – hole circle diameter of hub flange
w – distance hub flange to wheel center line
n – number of spokes
c – number of spoke crossings