A Guide to Scope Magnification: What Do Scope Numbers Mean?

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Have you ever wondered what the numbers on a rifle scope mean? These numbers can sometimes seem intimidating, and even deterring to a new rifle scope shopper.

Well, have no fear, all of your worries will be put to rest here.

Let’s jump in!

Where to find the numbers

First, let’s start by making sure you know where to find the all-important mystery numbers.

They are located in the name of the scope. For example, when you’re reading an article or shopping on Amazon, you’ll see a product name, such as the Leupold Rifleman 4-12×40. In that title, you can plainly see the numbers, “4-12×40.”

Now that you know where to locate them, let’s dive into what they mean.

What the numbers mean

The numbers on a rifle scope are indicative of the magnification power and objective lens diameter of the scope.

Let’s break that down into their two respective parts.

1. Magnification Power

First, we will look at magnification power. The first set of numbers (everything before the “x”) is indicative of how magnified your target will be when looking through the scope.

So, for example, if your scope is 4x magnification, that means it has one magnification setting that allows you to see your target at four times larger than its real size. This type of scope is called a fixed scope because it has one fixed setting.

Likewise, if your scope is 4-12x magnification, that means your scope is adjustable and you can see objects anywhere between four and twelve times larger than their normal size. This type of scope is known as a variable scope.

Now, let’s look at the objective lens diameter.

2. Objective Lens Diameter

The number behind the “x” is the objective lens diameter, and it is measured in millimeters (mm).

So, for example, if it says “40” behind the “x” in the name of your scope, that means the diameter of your objective lens is 40mm.

The measurement of the objective lens diameter indicates how much light can enter into the scope. The larger this size, the more light it allows to enter, thus making things appear brighter and more visible in low-light situations.

Now that we know what the individual numbers mean, let’s give you a couple of examples so you can see the whole picture.


1. If a scope says “4×32,” it means the scope has a fixed magnification setting that displays your target at four times its normal size, and the objective lens diameter is 32mm.

2. If a scope says “4-12×40,” it means you can adjust the size of your target between four and twelve times its normal size, and the objective lens diameter is 40mm.

By now, you should have a pretty good handle on how to read rifle scope numbers. Once you find the perfect scope to fit your needs, you can start doing the fun stuff like mounting, sighting in, shooting, and most fun of all… getting bullseyes!

Happy shopping!

One last note: if you’re looking for the best Leupold rifle scopes, check out my guide on that.


What to consider when buying a rifle scope? 

If you want to see a whole lot of things in a very tiny space, then a fixed magnification is going to be your best choice. However, if you want a scope that comes with a lot of flexibility, then a variable power or variable magnification is going to be your best choice. 

These aren’t the only factors to consider before buying a scope though. There are many other things, such as what type of shooting you plan to do, what kind of gun you have, how much versatility you need, MOA or MRAD, whether you want first or second focal plane, etc. 

How do you calculate the zoom range of a scope?

The formula for calculating the zoom range is:

Where: V = Variable power or variable magnification

Number of Exposed Pixels = Objective lens diameter (mm) x Zoom Range (mm/pixel) = Total number of pixels in your scope. 

What other numbers are associated with the scope? 

There are two other numbers associated with the scope. The first is the diameter of the lens in millimeters, and the second is the amount of light that can enter the scope (measured in foot candles).

These numbers can be found on your scope right before you get to “Mil Dot Range-Finders.” The diameter of the lens is measured by millimeters.

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