How to Read Scope Numbers and Their Meaning

No one scope can perform extremely well in all circumstances. This has, therefore, led to the manufacturing of different scopes to offer various services. Although the primary aim is to provide users with reliable vision and facilitate accuracy, the difference is quite essential. With this, it is good to know how to read scope numbers and their meaning

Therefore, if you are considering getting a scope for your rifle, then you need to understand various issues before making your decision.

First, you will notice that scopes have numbers labeled all over. Each number has its meaning and is significant in how the scope performs.

Before making your decision, it is vital to understand each number and what it means.

This way, it will be easy for you to make the right choice and invest in a scope that will enhance your operations. In this blog, we will discuss different numbers on the scope and what they mean.

Video showing How to read scope numbers and their meaning

Issues That Affect the Numbers

How to read scope numbers and their meaning entails numbers. To truly understand what the numbers mean within the rifle scope, you must understand what they represent and how these representations affect your choice of scope.

There are two sets of numbers on the rifle scope that genuinely matter. The first set stands for the magnification of the rifle while the second is the distance, which is the diameter of the objective lens.

Magnification is a physical property of the scope, and it is defined by the curvature, the thickness, the material used, and the diameters.

In some cases, the coating selected will also affect the magnification.

Once the physical characteristics are well understood, it becomes easier to set the equation, which will define the property of the lenses. The lenses have three main uses:

  • They are great at magnifying the targets. They do this by capturing the light through the objective lens and reflecting it from the target.

This light is bent to create a larger image of the target. The more expensive scope options will utilize several lenses to give you a clearer view of the magnified object.

  • The lenses also invert the larger image. Once the image is produced by the objective lens, it is often inverted. There is an erector that has two lenses that will flip the image, so it is easier for you to see and understand it.
  • You can also use the lenses to focus on the image. Lenses with higher eye relief are better since they make it comfortable for you to see the image when it is fully focused.

The Magnification

This is the first number that appears on the scope. The initial numbers show the lowest magnification while the second shows the height of the image.

Scopes that have a fixed magnification will only have one number. For instance, a scope with the numbers 4X40mm shows that the target in the scope’s reticle will be four times closer than the actual distance.

The numbers will always be separated on a scope that has variable power such as 3.5-19X, a feature that is common with most of the modern rifle scopes.

This variable power allows you to enjoy greater versatility and capability from the scope you buy for yourself. As a hunter, this is one of the best features to look for when buying.

The image that is viewed through the ocular lens is only an image, and the reflection is not the reality itself.

There is a great relationship between the target and the image, which is proportional and linear.

The magnification, in many instances, defines the ratio between the focal length of the objective lens and the focal length of the ocular lens. The magnification tells you how the images will be different from the target.

For instance, if your rifle has a magnification of 3X, it means that the image you are viewing will appear that it is 3x closer than its actual distance.

Therefore, if your target is at 300 yards, the magnification will make it appear as though it is only 100 yards away.

The more the magnification increases, the more the apparent distance to the image increases in direct proportion.

This will double the magnification from 3X to 6X, which will cause the target of the images to appear as though they are half as far as they actually are.

Additionally, the height of the target will also increase as the magnification increases.

This means that if the magnification doubles to 6X, it will halve the apparent distance to the target while doubling its size. The images will look as though they are bigger and closer.

Choosing the power that is most appropriate for you will depend on the environment and the distances you expect. Of course, if you are shooting at moving targets, you will not choose the same power as a person who shoots at still objects.

The magnification will affect how moving objects appear. Higher magnifications mean that you may be unable to see the targets.

Also, if you are operating in mountainous areas for a long-range environment, the rifle with a variable power or a high fixed power will be perfect. It will give you the clear image you need for a smaller target even if it is hundreds of yards away.

Size of the Objective Lenses

This is the last number on the sequence and represents the objective lens. This is always measured in millimeters. It shows the diameter of the objective lens.

For instance, if your scope shows 3-9X40, it means the scope has a variable magnification of between 3X and 9X, and the objective lens has a diameter of 40mm. The objective lens is that which is closest to the target, and it is also furthest from the stock of the rifle.

Larger lenses have a higher capacity to let light in, which means the target is clearer. These are perfect for people who hunt in low light conditions.

The more the magnification of the scope, the larger the objective lens should be to allow the scope to maintain a higher level of clarity and brightness.

How the Scope Works

For you to fundamentally understand all the numbers and what they mean, then it is essential to understand how the scope functions.

For starters, a scope has four main components: the optical coating, glass, eye relief, and parallax adjustment. Therefore, while understanding how it works, looking at each element is critical.

The Eye Relief

Eye relief refers to the physical distance between your eye and the scope without losing sight of the image entirely. This often varies depending on the power of the scope while mounted on a rifle. Therefore, it is essential to find one that has a friendly eye relief for enhanced performance.

Additionally, finding a scope with generous eye relief, it allows you to effectively pick your target and enhance your shots, especially while your target is moving.

It also ensures to protect you from getting a scope eye when your rifle recoils. This is a consideration to make when learning how to choose binoculars for birding.

Glass (The Lens)

The commonly used in making scopes are the high-definition glasses or the extra-low dispersion glass (ED glass).

The lens is responsible for directing the external light to the focal point to increase sharpness, clarity, and colors to objects.

It ensures that your image is precise and close to accuracy as possible.

Parallax Adjustment

Parallax adjustment is the top knob on the scope that helps in adjusting the reticle. This is the series of lines in the eyepiece, which measures the size of distant objects.

It mostly occurs when you are view objects at a distance with 10x magnification or more. The reticle appears to shift or change hence pushing the scope reticle to a similar focal plane with the target.

Therefore, to correct this, you will require to use the parallax adjustment to align the reticle for a better shot.

Additionally, those without the adjustable objectives can always preset their scope for a better focus at approximately 150 yards.

Optical Coating

The main purpose of the optical coating is to minimize reflecting light while you are using the scope. On average, 1-5% of light reflects on the glass surface. This, therefore, blurs the images and also decreases the amount of light transmission for clarity.

Therefore, manufacturers use multiple layers of coating to ensure limited light loss for vibrant and clear images.

Different brands may use a unique name to speak of optical coating on their scope. This is commonly in the bid of ensuring they capture the attention of buyers.

An optical coating is popularly known with three types:

  • Coated– This is commonly done on the exterior surfaces of the glass. It helps in protecting your lens from abrasion.
  • Multicoated– It helps reduce glare and prevents your glass from abrasion. The multi-coating is also applied on the exterior surfaces of the glass.
  • Fully multicoated– This is applied thoroughly on all glasses, both exterior and interior. It helps in maximizing durability and enhance light transmission.


How to read scope numbers and their meaning is quite essential. They bring a great difference in the way to eye your target and make your shots. Therefore, knowing how to read and understand them comes in handy.

It enhances your performance in the field as well as gives you confidence while you take every shot.

Therefore, for you to adequately understand the difference, take your time to familiarize yourself with the scope and practice as much with target shooting.

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