What Do the Numbers on Binoculars Mean?

The numbers on binoculars essentially tell you their strength (magnification power) and size (objective lens diameter).

A “10×50” for example,

  • Magnifies the view by 10 times, Objects appear 10 times larger than they do without the binocular.
  • The second number refers to the objective size (diameter in millimeters).

How to choose numbers with a Slash Or Dash?

  • Slash ( / ): Suppose “25/40×100”, If the numbers are separated by a “/”, then the binocular is not a zoom, but uses multiple fixed-power eyepieces to obtain different levels of magnification. A 25/40×100 Long-Range Observation binocular has 25x and 40x eyepieces on rotating turrets, so you can easily switch back and forth between 25x and 40x magnification.


  • Dash ( – ): Similarly “12-36×70”, When there is more than one number before the “x”, this means the binocular has multiple levels of magnification. If the numbers are separated by a “-“, such as “12-36×70”, then the binocular is a “zoom”, and the magnification is continuously variable from the first number to the second number (in this case, 12x to 36x), by moving a zoom lever.


Objective lens size gives you an understanding of how physically big the binoculars are and how much light they can gather.

The size of the objective lens will determine how much light the binocular can obtain for effective viewing.

NOTE: Binoculars using multiple fixed-power eyepieces do not suffer from the optical limitations of zoom binoculars.

I hope this article has helped you understand those pesky numerical product descriptions. Hence, Enjoy Shopping for Binoculars without confusion!

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