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What Do The Numbers Mean On A Scope?

What Do The Numbers Mean On A Scope
Written by Dan Goldsmith
Last Update: August 11, 2023

If you have ever seen a scope, you must have seen some numbers on it. But what are those numbers? What do the numbers mean on a scope?

The numbers on a scope refer to its magnification power and objective lens size. For example, a scope described as 3-9×40 means it has a variable magnification range of 3x to 9x and an objective lens diameter of 40mm1. Additionally, other numbers on a scope can refer to eye relief, MOA, parallax, length, weight, tube chassis, and field of view

However, with so many different numbers and specifications on a rifle scope, it can be challenging to understand what they all mean.

In this blog post, we will break down what the scope numbers mean and how can understand the numbers and measurements to pick the right scope for your needs.

What is a Scope?

The sighting device that shooters mount on their rifles or firearm is called the scope. It enables the shooter to aim accurately by magnifying the target. Shooting accuracy is further increased with the crosshair or reticle inside the scope.

These devices come in different types and sizes. Their specifications and features differ depending on the model.

Components of a Rifle Scope

A rifle scope consists of the following main components:

  • Objective lens: It is the front lens that gathers light and creates the image.
  • Magnification ring: The adjustable ring that allows you to change the magnification level of the scope.
  • Turrets: These are the knobs that allow you to adjust the reticle for elevation and windage.
  • Eyepiece: The rear lens that focuses the image and allows for eye relief.
  • Reticle: The crosshairs or other markings on the scope that are used for aiming.

What Do The Numbers Mean On A Scope?


Arguably the most important number on a long range rifle scope is the magnification. It determines how much closer you will see  your target when you look through the scope. Rifles can have variable magnification or fixed magnification.

Variable scopes allow the shooter to adjust the magnification level as needed. This means, if you have a scope with magnification range of 3-9X, you will be able to adjust the magnification level from three times closer to nine times closer.

On the other hand, as the name suggests, fixed magnification has only one or fixed magnification setting. And the numbers on a fixed magnification scope looks like this: 4×32. The number 4 before the “x” indicates that you will see your target four times closer than its normal size. Now, what does the 32 after the “x” mean?

Objective Lens Diameter

The objective lens diameter is the second number that is commonly listed on a rifle scope behind the “x”. It is the diameter of the front lens in millimeters.

So, for instance, if you see the number 32 behind the “X”, that means 32mm is the diameter of the scope’s objective lens.

A larger objective lens allows more light to enter the scope, which can improve image quality and brightness. However, a larger objective lens also means a heavier and more expensive scope.

Reticle Measurements

Another measurement you may notice in your scope is of the reticle. It is of the markings or crosshairs that you use for aiming. There are several types of reticles available such as mil-dot, duplex, and bullet drop compensator or BDC. You may come across the following reticle measurements:

  • MOA (Minute of Angle): This is a unit of angular measurement that is used to adjust the turrets for windage and elevation.
  • MIL (Milliradian): This is another unit of angular measurement that is used for the same purpose as MOA.
  • BDC: This reticle is designed to compensate for bullet drop at different distances, allowing the shooter to aim without having to adjust the turrets.


If you know how do scope numbers work, and understand what do the numbers mean on a scope, you will be able to pick the best scope for yourself. In addition, you will be able to ensure optimal use of the scope if you know these tiny, yet vital details. You can greatly improve your shooting skills and accuracy if you combine this knowledge with practice. Knowing how a scope works is very important for a good shooting experience.


Q: What does the numbers 3 9×40 mean on a scope?

A: If you see the numbers 3 9×40 on your scope, this means it has a variable magnification range from 3x to 9x and it has a 40mm objective lens diameter. So, on the basic setting, you will see any image 3 times closer with this scope and 9 times closer with the highest setting.

And in terms of the objective lens, the larger it is, the brighter the image will be.

Q: What are the 3 numbers on scopes for?

A: The 3 numbers on a scope refers to the magnification and objective lens size of the scope. For example, if you see 3 numbers like, 3-9×40, the 3-9 is the magnification range of the scope and the 40 is the objective lens diameter.

Q: Which scope is better 3 9×40 or 4×32?

A: The choice between a 3-9×40 and a 4×32 scope depends on what purpose it will be serving. The former is a good choice for general shooting and hunting because of its variable magnification range. This will allow you to adjust for different shooting situations.
A 4×32 scope, on the other hand, is the ideal choice for long-range shooting and precision shooting. Due to its fixed magnification, it can provide more precision when compared to other scopes . Ultimately, the best scope for you will depend on your specific needs and preferences.

About the author

Dan Goldsmith

Hi, this is Dan. We all know firearms are dangerous, but only when one doesn’t know how to use and care for them. I have 30+ years of experience with different types of guns and for the last 10 years, I have taught numerous people how to hold and shoot a gun while staying safe and keeping the surroundings unharmed.

My neighbors are some of my biggest admirers who enjoy talking to me about their guns, firearms safety and maintenance.

Whenever I am able to catch a moment of free time, you will find me enjoying my family or heading to the range on my motorcycle. I have enjoyed shooting sports ever since my dad introduced them to me as a child.

I like to think of myself as an outdoorsman who lives his life to the fullest. I hope you will benefit from my efforts to create valuable resources on this website. Happy reading!

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