What is the normal size of a cucumber?

A cucumber can grow anywhere from a couple inches, to several feet. It really depends on the climate, dirt, gardener, etc. All sorts of environmental factors go into determining how tall (or long, as the case may be) of a cucumber.

Or, if you have it on it's side, then the height is probably a few inches. It all depends on how you look at it.

My advice would be to purchase, or grow a cucumber, and measure it yourself.