The magnification factor, also known as "power", is listed as the first number given in a binocular's name, like 7 x 50, 8 x 40, etc. In the first example, these binoculars magnify an image 7X more than if you were looking at that image with the "naked eye". When talking about zoom binoculars, the magnification is listed like this: 7-21 x 50. That means the binoculars have a zoom mechanism that takes the power from 7X to 21X as far as the eye can see. Please note that it doesn't matter whether there is spacing between the numbers or whether the "X" is upper- or lower-cased.

Don't always assume that more magnification is better! The more power, the harder it is to keep the image stable when hand-holding binoculars. Most people can comfortably hand-hold up to an 8X (most popular for birding), but after that, you may or may not need a tripod for a shake-free view...it depends on your own steadiness and how long you plan to view.