What does the X Number on a Zoom Camera mean?

The X number is the zoom ratio of the lens, used to measure the difference from the wide to narrow extremes of the lens. You will see it listed in advertising as a number followed by an X, such as 3X or 10X. The zoom ratio is not necessarily the magnification power of the lens, simply the range in adjustable magnification power of the lens.

Zoom ratio is simply the value of the longest focal length of the lens divided by its shortest focal length. So, the zoom ratio for a 20-500mm lens is 500mm ÷ 20mm, or 25X. Note that if you had a 5–500mm lens, it would have a zoom ratio of 100X, however a 500mm–1000mm lens would only have a zoom ratio of 2X despite it having double the magnification of ability of the 500mm lens at full zoom.