Travel per turn
A point on the pinion's pitch circle travels pi x d in one revolution, and because the teeth cannot slip, the rack moves the same distance. With an 18 mm pinion that is about 56.5 mm per turn of the steering wheel.
The road wheel angle here assumes a 150 mm steering arm and uses atan(rack travel / 150 mm). Real suspension geometry, including the Ackermann layout that turns the inside wheel more, makes the true angles a little different, so treat it as a teaching estimate.
Try it: set the pinion to 12 mm and turn the wheel a full 360 degrees. The rack moves about 38 mm and the wheels turn about 14 degrees. Switch to 30 mm and the same turn moves the rack about 94 mm and the wheels about 32 degrees.
Beyond steering
The same pair turns up in rail systems that climb steep grades, in machine tool slides, in gates and in linear actuators. Power steering adds a hydraulic or electric assist on the rack but leaves this geometry unchanged.