What do the numbers on binoculars mean? Explained


Whether you have bought the binoculars without understanding what do the numbers on binoculars mean? Or, you already have bought them and now wondering how to decode these numbers to appear on the binoculars? Well, we have explained the numbers on binoculars in detail so that the user no longer wonders about the formula to calculate these numbers.

Without any delay let’s take a plunge and explain “what do binocular numbers mean?”


8x42, 10x42, 10x32, 10x26 , 10x50, 12x56...

So what exactly do these numbers mean on binoculars? What do they tell us about a binocular and which one should you get for your desired use?

At the most basic level, the main purpose of any binocular is to magnify the view and thus bring distant objects more clearly into vision by making them appear closer or larger. Thus it stands to reason the most important thing to know about a binocular is how much it magnifies the view and indeed how much magnification you need for what you intend to use them for.

Luckily for us, manufacturers make the first part of this easy as almost every binocular has the magnification included in its name so for example, when you see 8×42 in a binocular the first number before X is the magnification. So the binoculars with 8x magnification will make whatever you look at through them seem 8 times closer or larger. 10×50, 10×42, 10×32 or even 10×26 binoculars will all magnify the image by 10 times.

Magnification Power- NumberX




Exactly how much magnification you need or the ideal amount for your intended use is a little more tricky to get right as it depends on a whole bunch of other factors but what is important to note is that bigger is not always better. A good rule of thumb is that for general users an 8 times or 10 times magnification is probably going to be perfect.

Steady Images:

At high magnifications (12x and up) it is difficult to maintain a steady image unless you have the binoculars stabilized on a solid object like a tripod, table, or a wall. Or if you have stabilized binoculars. You also get zoom binoculars, which offer an adjustable magnification range.

A Dash? Zoom Binoculars:

For some binoculars between the first two numbers, you’ll see a dash for example 12-40×40. The dash indicates that the lens can be zoomed. 

Zoom Binoculars work on the same principle as standard or regular binoculars except that the magnification power can be adjusted to give you different ranges of magnification. 

For example, binoculars having 10-22x50mm means the device is capable of viewing at 10X  magnification minimum and can be adjusted up to 22x power. There lie strengths and weaknesses to zoom designs.

Although zoom binoculars allow you to quickly zoom in and out, which is a particularly nice feature for hunters, since you can zoom in to see fine detail, then zoom out quickly to track the animal if it changes its position. But on the other hand, the zoom mechanism adds weight and bulk to the device.

As mentioned an important thing to keep in mind about magnification is that more isn’t always better. The more you zoom in the smaller your field of view is going to be.

For 12-40×40 binoculars, a 12x zoom is going to fill the entire field of view. As you zoom in more, the image will appear closer but the area covered from the lens of your binoculars will get narrower and narrower. Usually, a lower zoom is great for spotting flying birds or distant deer.

But the advantage of a high zoom can’t be neglected. Well at 40x, for example, you can see a rabbit clearly from nearly 300 or 400 yards away. But you’ll need to know where it is, first using low magnification and when spotted you can zoom in for further and minute details.

Also with high zoom, images will appear dim, because, at higher zoom, the lens is only able to capture a certain amount of light. Always remember, the narrower the field of view, the less overall light will pass through the lens resulting in less vibrant colors. 

Number after X - Objective Lens Diameter


Right next the number that comes directly after the magnification (numberX) on a pair of binoculars indicates the size or diameter in millimeters of the main objective lenses. 

These are the bigger lenses on the ends of the binoculars so for example a binocular with 8X42 written on them has 42 millimeters diameter objective lenses. Whilst 10×42 will have the same size lenses 42 millimeters but with a higher 10 times magnification.

The 8×32 has smaller 32 millimeters objective lenses and those on the Swarovski CL 8×25 are only 25 millimeters.

The size of the objective lenses on binoculars is important in many ways. Firstly it plays a major factor in determining just how large the binocular will be. The larger the lens the bigger, heavier the binocular.

If this is the case why would you want larger lenses?

Well, a good way to think of it is like looking through a window. A larger window lets in some more light than a smaller one versus the same with lenses; the increased surface area of larger objective lenses means that they can capture more light. Thus it plays a critical role in determining the brightness or more accurately the low-light performance of binoculars.

 For zoom binoculars (10-22×50) the 50mm would be the objective lens size (the larger lenses at the opposite end of the binocular). When considering zoom binoculars remember that a larger objective lens would far better give you the greatest amount of light-gathering, but they will be bigger and heavier. 

Once again the larger the objective lens, the more light it’s going to let in. The more light it lets in, the brighter the image, and the more vibrant the colors you will see. If your activity is say bird watching then large lenses will allow you to better enjoy bird’s plumage.

On the other hand, the objective lens is the heaviest part of your binoculars. The binocular tubes can be made of lightweight aluminum and the rest of the parts can be made of plastic or rubber etc. But for lenses, there’s no replacement for high-quality optical glass, which is a sturdy material.

For astronomy light gathering and low light performance are much critical, consider buying binoculars having large 100mm lenses or even more in some cases. But do not forget to get a tripod as well because using large aperture binoculars without a tripod is not the best idea.

Full-Size Binoculars:

42 mm or above are the full-sized binoculars having a good balance between the size and light gathering ability. Guaranteed to provide stunning views on bird watching, hunting.

Mid Sized Binoculars:

30mm to 32mm are considered mid-sized binoculars. Gives you amazing results during the day and fair.y portable but for low light performance, these are not the right choice.

Compact Binoculars:

18mm and 28mm are usually referred to as compact binoculars. Best transportable and pocket-friendly option. Ideal for hiking, camping, nature watching taking to outdoor sporting events, walking safaris, etc. Though do not provide the best performance in low light conditions.

Angle of view (AoV)

Angle Of View


The angle of view and the field of view refers to the same thing. This means the amount of visible horizontal scenery when looking through the binoculars.

Let’s discuss them separately for better clarity, also we will tell you how you can convert one to the other.

The angle of View is abbreviated as AoV. It is measured in degrees. The bigger the number, the wider the area you will see. AoV over 6 degrees can be considered a reasonable angle of view.

Multiplying the angle of view in degrees with the magnification value of the binoculars gives you the actual angle of view. For example, 10×50 binoculars with a 7.2-degree angle of view will have a 72-degree actual angle of view (7.2 x 10 magnification).

Magnification x angle of view in degrees = Actual Angle of View

Field of View

Field of view


Field of view is abbreviated at FoV and expressed or measured in feet per 1000 yards Or meters per 1000 meters. Not all binoculars display these numbers, but they’re worth mentioning. FoV number can be written in several ways, but the most common way is to express the width of your view at 1000 m. So 120/1000 binoculars will have a field of view that’s 120 meters wide at a distance of 1000 meters.

The high number means you can observe a wide area with binoculars. An FoV of about 300 to 375 feet is adequate. Remember:

Lower magnification = Greater field of view

Higher magnification = Narrow field of view

This means the higher your magnification, the smaller your field of view will be due to the object being closer.

How do you convert the angle of view to the field of view?

Multiply the angle of view by 52.5

So, a 7.2-degree angle of view equals a 378 feet field of view

7.2 x 52.5 = 378

If you’re looking for the prey on your hunting adventure you’ll want a wide field of view to have a better chance of spotting it. With a narrow field of view, you’ll need to pan the binoculars around more and may miss the target you’re searching for. Hence consider a good balance between magnification and field of view.

You might be thinking having a bigger lens means having a bigger field of view, yeah? It’s the opposite. The bigger your binocular’s objective lens the smaller field of view you’ll have. For general use, you should find a good balance somewhere between 38-42mm. This will give you a reasonable field of view while allowing enough light to enter. The wider the field of view, the more you can see.

Eye Relief Number

Eye Relief


If you wear glasses eye relief becomes one of the most important features to be considered.

Eye relief is the maximum distance away from the viewing lens (eyepiece) in which you can enjoy and see the entire magnified field of vision (field of view).

So in case, you need to wear your glasses to see through your binoculars, try to find optics that has enough eye relief to accommodate your eyeglasses. Eye Relief of 15 mm or above is considered adequate.

Exit Pupil Number


You might have noticed two dots in the center of the eyepieces if you hold your binoculars away from your eyes. From these dots, light from the lenses hits your eyes to enable you to see the image you’re focusing on.

A rule of thumb is exit pupil has to be greater than your eye pupils and anything above 4mm would be enough for most of the activities, but wider is always better. The wider the eye relief, the more light will be registered by your eyes when using the binoculars. This can actually vary from person to person. 

This number is not written on the binoculars but can very easily be calculated by using a simple formula: Dividing the objective lens diameter by the magnification.

Objective lens diameter/ Magnification = Exit Pupil

For example, an 8×25 will have a 3.1mm exit pupil.

Close Focus

This number tells you the minimum distance the binoculars can focus on. The shorter the close focus distance, the more one can focus on details that are not visible to the naked eye. For example, a close focus of 10 feet means you can get a clear focus on an object as close as 13 feet to you. This is best for detailed viewing mostly insects and butterflies. A close focus distance of less than 6.5 feet / 2 meters is just perfect!


We have revealed the surprise hopefully, you’re no longer wondering, what do the numbers on binoculars mean? A summary to help to remember the key points:

  • The greater the magnification smaller is the field of view.
  • For astronomy or low light, viewing considers a large objective lens diameter.
  • If portability is the concern consider a smaller objective lens diameter.
  • Eye relief for 15mm or above if you wear glasses.
  • An ideal exit pupil is more than 4mm.
  • Minimum close focus distance if you want to magnify very close objects.
  • Magnification above 12x would give blurry images without (tripod) support.

I hope you have found this article informative as it should cover everything you need to know when buying binoculars.

4 thoughts on “What do the numbers on binoculars mean? Explained”

  1. Hello there I am so thrilled I found your blog page, I really found you by accident, while I was searching on Aol for something else, Anyways I am here now and would just like to say many thanks for a tremendous post and a all round interesting blog (I also love the theme/design), I don抰 have time to go through it all at the minute but I have saved it and also included your RSS feeds, so when I have time I will be back to read more, Please do keep up the superb work.

  2. Youre so cool! I dont suppose Ive learn anything like this before. So nice to find somebody with some authentic thoughts on this subject. realy thank you for beginning this up. this web site is something that’s needed on the net, someone with somewhat originality. helpful job for bringing one thing new to the internet!


Leave a Comment