It's very hard to explain how they translate, honestly. Pictured, the Eagle (little wheel in the front) is a 50", the ordinary is a 52" [diameters]. The wheels also have about an inch added from tire. That * pi = one pedal rotation's wheel rotation, or your gear inches, but because it's direct drive, it's harder to pedal. You're looking at 161" and 166" gear inches, respectively (or nearly 14 feet traveled per pedal rotation). It's fun counting pedal rotations while climbing, and realizing how long a specific hill was.

People try to compare it to a fixed gear, and while you can get close, the physics of direct drive, aerodynamics and simply posture make a modern bike much "quicker". Add in very short cranks, flats with no clips/clipless, the fact that these specific ordinaries weigh around 60-70lb (there were light roadsters in the 30 range, and racers in the 20s, but they are rare and delicate) and a single hand position - I think you know what I'm getting at.