What do the numbers on the scope mean?

    It’s absolutely normal for question to cross your mind the first time you are browsing for a rifle scope… or any lens in general, really. As your eyes fall on the description that reads “3-9×40” or “3×32” you may feel like you are reading a whole different language! The second question you surely may ask yourself is: “how do I know which one is for me?”

    No worries, we’ve got you covered!! In this article we will explain, in the simplest of manner, what those numbers mean and why they matter when you are choosing your next scope. For our first example we will use the 4×32 scope and the 3-9×40 scope, but keep and mind that what you learn here can be applied to the optics of your choice like a 4×20 or a 2-7×32, etc.

    What does 3-9x40 on a rifle scope mean?

    How to interpret the numbers on a rifle scope

    First thing is first, we will dissect these digits and in order to explain each one and facilitate this learning process. The following two lens will be our examples:

    • Scope 1: 4×32
    • Scope 2: 3-9×40
    What does 3-9x40 on a rifle scope mean?

    Magnification or Zoom

    Note: you will find that there is always an “x” separating two sets of numerals.

    The following shows the numbers that are to the left of the “x” in our previously mentioned examples:

    • Scope 1: 4
    • Scope 2: 3-9
    numbers that indicate a rifle scope’s magnification

    They refer to the lens’ magnifying capacity or in other words, the scope’s ability to “zoom in”. This is how you should read them:

    Scope 1 has a magnifying capacity of 4.” This means that through the lens you will visualize the target four times larger incomparison to the size which you see with your naked eye (the image is larger through the lens).

    What does 3-9x40 on a rifle scope mean?

    When is a lens adjustable and when is it not?

    Looking at Scope 2’s magnification you may ask, “So why does it have a dash?” That’s easy.

    When the numbers to the left of the “x” are separated by a dash (-), this means that our scope’s zoom is adjustable. This is how you should read it:

    Scope 2’s magnifying capacity can be adjusted to range from 3 to 9”. Its minimum magnifying value is represented by the number to the left of the dash (in Scope 2’s case it’s 3) and its maximum value can be identified as the number to the right of the dash (in our example it’s 9).

    adjustable/varying magnifying capacity 3x9x40

    It is worth mentioning that there are values in between 3 and 9 that can also be used (4, 5, 6, 7, and 8) to optimize your focus on the object based on the distance between you two.

    magnification or zoom levels of a 3x9X40 lens

    Altogether, our example’s will be read as following:

    • Scope 1: 4×32 (Nonadjustable lens that has an objective magnification of 4)
    • Scope 2: 3-9×40 (Adjustable lens who’s objective magnification is 3-9)

    The objective lens’ diameter

    Now that we know what the numbers to the left of the “x” signify, it’s time to turn our focus to the numbers on the right. Simple.

    The numbers to the right of the “x” refer to our scope’s frontal lens’ (also known as its ‘objective lens’) diameter, expressed in millimeters. Back to our example:

    • Scope 1: 32 (the frontal lens has a diameter of 32 mm).
    • Scope 2: 40 (frontal lens has a diameter of 40 mm).
    what do the numbers on the right mean to a scope lens?

    In conclusion, said numbers represent the objective lens’ size.

    Why does our objective lens’ size matter?

    In general, the larger a frontal lens’ size is permits a greater amount of light to enter the optic system and the more light that enters system consequently amplifies the user’s visual field. In conclusion, the larger diameter your objective lens possesses, the farther and better you will be able to see. This is fundamentally useful during the hours where there is minimum daylight, like at dawn or dusk.

    This concept has its pros and cons and its downside is that it that since your scope increases in size, it and therefore your rifle, will increase its weight as well. This is problematic when the weight interferes with your attempts to shoot while standing.

    How to interpret the numbers of a scope

    Let’s re-read our examples with our new found knowledge and finally make sense of our scopes:

    • Scope 1: 4×32 (Nonadjustable scope with magnification of 4x and an objective lens that is 32 mm in diameter).
    • Scope 2: 3-9×40 (adjustable scope with a magnification of 3-9x and an objective lens that is 40 mm in diameter).

    There’s an additional plus to learning all this! Now you can apply this reading criterion and understand any type of magnifying optical instrument, whether it be adjustable or not like in the case of a telescope or binoculars.

    How far can I see with telescopic sight?

    We are occasionally asked: “how far can a 4×32 see?” Technically there isn’t a way to measure this because these optical system’s function is to magnify and not to help the user to see further . Their job is to enlarge the target and that is why it appears to be nearer than it really is. Your job, as the user, is to use that magnification as an aide when making decisions.

    “Can a 4×20 rifle scope allow me to see a deer that is 200 meters (218 yards) away?” The answer is yes, of course. But what you should really be contemplating is: how big or accurately do you want to see that deer? This is what you should be asking yourself when you are decided to use a 4×32, a 3-9×40 scope and/or any magnifying element that you may have at hand.

    In order to assure that you, the reader, understands the concept of magnification we decided to add one last helpful example: Imagine that in the distance you see and object and you take a picture of it. You decide to measure the size with a ruler and find that it is 2 centimeters (0.8 inches) tall. Next you proceed to take the same exact picture of this object, but this time through a lens that has a magnification of 2x. This time, the object will be larger in the picture. How much larger? Two times larger! Therefore when you measure the object once more, its size in the new picture will now be 4 centimeters (1.6 inches) tall.

    With that being said, when you are choosing a new scope you must first ask yourself the following two questions: What is it that I want to see? How much do I need to magnify it in order to see it as clearly as I want?

    What is the range of a 4×20 scope?

    A 4×20 scope is recommended for distances between 50 and 100 meters.

    What is the range of a 4×32 scope?

    A 4×32 scope is recommended for distances between 50 and 100 meters.

    What is the range of a 3-9×40 scope?

    A 3-9×40 scope is recommended for distances between 150 and 250 meters.

    Which scope do you recommend me to buy?

    Start with something cheap but that allows you to climb. 3-9×40 riflescopes, as we saw, they can serve a myriad of purposes, both precision shooting and hunting. Start with that and then think of something higher magnification. I leave you my recommendations below.

    Best 3-9×40 telescopic sights in 2023-2024

    These are the 5 best-selling 3-9×40 scopes on Amazon this year. They are of good quality and decently serve their purpose in my opinion.

    Best 4×32 riflescopes in 2023-2024

    These are the 3 best-selling 4×32 scopes on Amazon this year .

    Best 4×20 scope in 2023-2024

    This is the best-selling 4×20 sight on Amazon this year.

    We hope this article was helpful! Let us know your opinion in the comments section.

    Good shots!

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