700c Bike Wheels Explained

700c Wheels: What the Number Actually Means

Bike wheel sizing terminology has gotten complicated with all the confusing numbers flying around. As someone who nodded like I understood when someone first mentioned 700c wheels — I didn’t — I learned everything there is to know about this topic. Today, I’ll share the explanation I wish I’d gotten earlier.

What 700c Actually Measures

Probably should have led with this section, honestly. 700c refers to wheels with a 622mm bead seat diameter — that’s the diameter where the tire sits on the rim. The “700” originally meant the approximate outer diameter in millimeters with a tire mounted. The “c” came from old French sizing that indicated tire width.

The terminology is a relic of historical tire sizing that no longer makes literal sense. Modern 700c tires vary in width from 23mm to 50mm+, but they all fit the same 622mm rim diameter.

Where 700c Shows Up

Road bikes, gravel bikes, cyclocross bikes, most hybrid bikes, and many touring bikes use 700c wheels. It’s the dominant wheel size for pavement-oriented cycling.

If you’re buying tires for one of these bikes, you’re almost certainly looking for 700c.

700c vs 29er

That’s what makes this endearing to us gear nerds — 29-inch mountain bike wheels (29ers) are the same diameter as 700c. Both use 622mm rims. The numbers are different because mountain bikes use inches while road bikes use metric, but the rims are identical.

This means some tires cross over, though most are designed specifically for one use or the other.

What Actually Matters

Match your tire size to your rim. 700c tells you the diameter. The second number (like 700x28c) tells you width. Make sure your frame has clearance for the width you want. That’s really all you need to know.