Hyperfocus. Do you?

[Shebang]

...For every focal length/aperture setting there is a focus distance that will give you an in-focus depth of field from 1/2 that distance to infinity...

I know how to get a specific aperture. But I don't know how to determine what the focal length is

...For instance: For a cropped sensor camera set at 50mm and f/11, the hyperfocal distance is 36.2 feet. If you focus on something at 36.2 ft, the first 18.2 ft (1/2 the distance) will be out of focus. From that point to infinity will be in focus.

How did you get 36.2 feet?