Everything you want to know about the Q Factor

What it is and why it matters, how to measure it, what the Q stands for, and more

Bird's eye view to show the crank length of an Ultegra crank arm on a road bike
(Image credit: Future)

As we all know, Q factor is the person who equips tuxedo-clad Special Agents with nifty double-0 gadgets as he chases after villains. Wait, no, that’s not right… In the world of cycling, the Q factor refers to the width of the crank arms. More specifically, the lateral distance between the outside of the crank arms at the point where the pedal spindles affix.

The name is actually derived from the word “Quack,” referencing the waddling gait of a duck. And no, I’m not joking this time. Cycling legend Grant Peterson coined the term during his time with Bridgestone Bicycles.

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