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What do the Numbers Mean on a Rifle Scope?

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Are you looking for a new rifle scope only to be confused by the various numbers and technical terms such as 20-60 x 80mm or 3.5” eye relief, etc.? Then you are in the right place.

Hey everyone, Jason here again, and today I have something for newbies taking baby steps into hunting and looking for their first scope. We are going to talk about the numbers on scopes and what they mean.

These numbers determine the magnification, lens size, eye-relief, etc. and since these define the performance of the scope knowing them is simply a must before buying a scope or you risk losing thousands of dollars.

So to help you make more informed buying decisions, let’s dig right into today’s topic.

What do Numbers Mean on a Rifle Scope

Numbers Mean on a Rifle Scope

Since the Vortex Optics Crossfire II 6-18 x 44mm is one of my favorite mid-range scopes I am mostly going to be using this as an example.

If you look at the name of the scope above it has 6-18×44. These numbers suggest the magnification of the scope where 6 is the minimum magnification and 18 is the maximum magnification.

Some scope can have magnification as low as 3 and the high-end ones like those from Trijicon come with a magnification of about 24 or more. 

You should choose the magnification range based on the distance you are comfortable shooting at. Long-range isn’t always the best way to go about it since it also costs much higher as it requires a better lens.

Talking about lenses,

44mm in the above example is the objective lens diameter which is always measured in mm. It varies from scope to scope and can be 50mm, 44mm, 42mm, 32mm, etc. with 50mm being the more widely used lens diameter

But how do I pick which lens diameter is ideal for me?

Well, if you are looking to hunt in low light conditions such as dusk or dawn, the larger the lens diameter the better it is for you. That is because it allows for more light to enter, in turn, ensuring you get clear visuals at all times.

Whether you are looking for a rifle scope or scopes for crossbows, the lens diameter is similar but compared to spotting scopes these have smaller lenses. That is because spotting scopes are designed for you to scope a wider area and have a much higher zoom of about 50 to 60x.

And at that magnification level, you need more light, especially at maximum zoom levels for clear visuals.

Even binoculars tend to have bigger lenses than rifle scopes or crossbow scopes as they are used for spotting as well but it is smaller than spotting scopes since they have lesser magnification.

That’s all about lenses and magnification. Let’s move onto the other bits.

Field of View

Field of view is often measured in Feet, Degrees, or Yards and is the amount of area you can see through the scope. As the magnification increases, the field of view decreases and vice versa. 

Lens manufacturers usually give FOV from a particular distance. For example, for the above-mentioned Vortex Optics scope, the FOV is 15.2-5.2 ft/100 yds.

If you believe you will be dealing with quick animals (oh those nasty deers) and need to acquire your targets in a jiffy then you want a scope with a higher field of view. 

Spotting scopes, once again, have the highest field of view as they are designed for you to scope targets before you aim and fire. Binoculars also have a bigger FOV as compared to rifle scopes.

In case you do not notice any change in the field of view with the change in magnification, it is called tunneling and is something you definitely want to avoid as it means the manufacturer has cut corners. This is usually why cheap scopes suffer from tunneling due to the poor quality of the lens. 

Thankfully, we at ScopeExperts try and test each scope before suggesting it so you do not have to suffer such issues.

Also, keep in mind that scope components aren’t always the reason for tunneling. Even mounting the scope wrongly can cause tunneling so make sure you mount your scope the right way and check every part in case you face this issue.

Eye Relief

Adjusting the eye relief

If you want to use the entire range of the field of view at your disposal you have to place your eye at a particular distance and the eye relief of the scope determines this distance.

Scopes with lower magnification have a larger eye relief whereas you’d need to get close to scopes with greater magnification.

For low-powered scope, eye-relief can vary from anywhere between 4” to as high as 6”. If you feel the gun has a high recoil then you want something with a higher eye-relief or you are likely to wake up with a black eye or worse.

Even if you are getting a high-powered scope ensure that the eye-relief is around 3.5” to 4”.

Eye relief with spotting scopes is much more up close and personal as these can vary between 16-17mm. But don’t worry since spotting scopes do not have any recoil. Plus, these scopes also include a special eyepiece that makes their usage comfortable.

The Vortex Optics scope comes with an eye relief of 3.7” which is acceptable. Some scopes like the UTG 2-7X44 which is also within the same price range feature a much higher eye-relief at 11″ – 9.5″ making its usage more comfortable.

Exit Pupil

The light from the scope also enters your eyes to give you a clear picture. And how much light leaves the scope depends on the exit pupil of the scope which is also measured in mm. And guess what, more doesn’t always mean better as all the additional light goes to waste.

And if the exit pupil is too small then your visuals are going to be blurry and dull.

The ideal exit pupil depends on the time you are going to hunt at. If you are hunting in low light, a larger exit pupil of about 7mm would be ideal as more light will enter the eyes giving you clearer visuals. 

But if you are hunting in the day, the bright sunlight means the diameter of your pupil will be no more than 2mm to 3mm.

Note: Not all manufacturers provide this detail so make sure you get in touch with them or the seller beforehand in case you want to know about it. The ideal thing would be to try out the scope before buying.

You can even calculate the exit pupil yourself. Just divide the diameter of the objective lens by the magnification provided by the scope.

For example, exit pupil for a scope with a magnification of 9 and an objective lens diameter of 60mm is 60 / 9 which equals 6.66 mm

Tube Diameter

Tube diameter is also measured in mm and comes in handy when you need to buy scope rings. It is usually 30mm or 40mm but you will come across various diameters as you dive deep into riflescopes

This is the diameter of the main body of the scope and does not have any impact on the optics of the scope.

Yes, unlike popular belief larger scopes do not allow more light in so do not fall for it. The one thing it does impact though is the windage and elevation range as a larger diameter means wider range.

Durability might also be more for these scopes but that also comes down to the material used in the construction (FYI, aluminum is the go to material)

Weight and Length

The weight of the scope is measured in oz or lbs. If you are looking to carry your scope in a bag or move around while it is mounted on your rifle, you want something lightweight so it doesn’t add to the overall weight. 

The weight of the scope is always listed by the manufacturer and so is the length. The more compact the scope the lesser space it takes on the rail. Plus, it is easier to store and carry as well.

These aren’t deal-breakers or the most important deciding factors as most scopes from popular brands like Vortex Optics, Trijicon, Bushnell, etc. are lightweight but since we are talking numbers, it is worth the mention.

For example, the Vortex Optics scope weighs 19.7 oz which is pretty lightweight. Some weigh around 7 oz as well and yet are durable.


Parallax is only something you need to worry about if your scope has a magnification of more than 10x as at higher distances the reticle tends to move. With parallax adjustment, you can get the reticle aligned with the target. 

To adjust the parallax, use the knob on the top. Some scopes have a side parallax adjustment so make sure you check the manual beforehand.

Since the Vortex Optics scope that we have used in the article has an 18x magnification it has a parallax setting of 10 yards to infinity


Minute of Angle (MOA) tells you how much a bullet can deviate as it travels over a long distance. 

On the other hand, MRAD means Milliradian and determines the angle at which the bullet needs to travel over a long distance for you to hit the bull’s eye. 

Since bullets never travel in a straight line, this measurement is important and can be tweaked using turrets. To learn more about them, check out the video below

A final word.

That’s all you need to know about scope numbers and how they impact the price and performance of every scope. Sure these can be complicated for any newbie viewing scopes for the first time but I am sure you won’t have any trouble now and will be able to make better buying decisions now.

In case you feel there are other numbers on your scope that are confusing you, feel free to reach out to me by leaving your doubts in the comment section below. You can also write to me via the contact page.

Don’t forget to include photos in the comments or email so I can better explain what the numbers are all about.

About Author

James Towndrow, a NRA-certified Firearms Instructor. During a career of 18 years had won several shooting competition including major leagues. Taking all those experience down the road, is now a successful Shooting Instructor in Texas, US.