What Do the Numbers on Binoculars Mean? Complete Guide 2023

By Richard

The important question that a seller asks is what configuration of binoculars you need. How will you answer if you don’t know what do the numbers on binoculars mean?

It is very important to know the number that explains the functionality and specification of binoculars. Only those who used binoculars at some stage of their lives know the meanings of numbers present on binoculars.  In this guide, we will provide you with in-depth knowledge about numbers and specifications present or written on the binoculars.

The brief model number written on the box of binoculars mainly represents magnification and objective lens. The first number before X is used to display the magnification strength whereas the second number that comes after X represents the diameter of the objective lens. For example, in 10X42 binoculars 10 is magnification power and 42 is the diameter of the objective lens which is measured in millimeters.

This question needs an answer in detail so let’s dive deeper to get in-depth details about the number and specification of binoculars.

Related article: 10X50 vs 20X50 Binoculars

Basic knowledge about what the number and specification of binoculars mean

Before going deeper and understanding the specification of binoculars, it is important to get the basic knowledge of numbers that are very important in showcasing the specifications of binoculars.

The main specification of binoculars depends on two numbers separated by X. For example 10X42 binoculars. 10 represents the power of magnification which means how magnified an image binoculars give to the users. The bigger the magnification number, the more magnified images will be shown to the users.

The magnification differnce between 8x and 10x binoculars
The magnification difference between 8x and 10x binoculars

The picture given above shows the comparison of two magnification powers (8x and 10x). The elephant appears less amplified with 8x magnification than at 10x magnification.

The second number in the specification represents the diameter of the objective lens. It is usually measured in millimeters and is considered a vital part of binoculars. The major function of objective lenses is to capture the light and show a brighter image. Different sizes of objective lenses are available in the market. 

Size of objective lens - how to understand the numbers on binoculars
Size of objective lens – how to understand the numbers on binoculars

Is it good to have a bigger objective lens?

Some newbies after reading reviews make up their mind that the binoculars with bigger objective lenses will give more quality images and hence they buy the binoculars with 50 mm of objective lens diameter.

It is totally a wrong practice as increasing the size of the objective lens increases the weight of binoculars. The optics with a greater diameter of the objective lens are bulkier than the binoculars with less size of the objective lens. 

It is worth noting that binoculars with less weight are more useful as they don’t make you tired. Choosing the normal diameter of an objective lens like 42 mm is more than enough to give a nice image. This size of the objective lens won’t make them heavyweight as well.

What is ideal magnification for outdoor activities?

It is another simple yet technical question that makes people confused. Many magnification powers are available in the market. But keep in mind that every magnification strength is used for a specific outdoor activity.  

Choosing 12x magnification for hunting is useless. Similarly, the 5x magnification will never work fine in birding. In hunting, you need less magnification and a greater field of view. But in birding, the field of view is not the point to talk about and everything is concerned with magnification power.

8x magnification is best for hunting as it gives an ideal field of view. At the same time, 12x magnification is good for birding as it gives a fully magnified image to observe every minute detail of the targeted object. 

For stargazing or astronomy, even high-powered magnification is needed as you will be seeing objects that are very far away from you. 

 A simple formula to remember magnification strength is given below

  • 8x will give you eight times bigger size of the targeted object
  • 10x will give a ten times bigger image than the actual size
  • 15x will give you fifteen-time bigger image than the actual size

Keep relating now by using the above formula of knowing what binocular strength means in binoculars.

In-Depth details of what specifications and numbers on binoculars mean & how to understand binoculars

Not only magnification and objective lenses but there are many other numbers that need an explanation to complete the answer to the question What do the numbers on binoculars mean?

Infographics explaining what do numbers on binoculars mean
Infographics explaining what numbers on binoculars mean

Understanding the numbers which describe the binoculars is very important. Apart from magnification and objective lens, the following numbers and factors are key in understanding binoculars.

  • Number Explaining Field of View
  • Coating
  • Number Explaining Close Focus
  • Type of Prism that a binocular uses
  • Number Explaining Eye Relief
  • weight of hunting binoculars
  • size 
  • Video ability of binoculars
  • Exit Pupil

Binoculars buying guide without mentioning any of the above elements is literally incomplete. We will dive deeper to understand more about choosing binoculars and all those numbers which are used to explain the specification of binoculars.

Field of view

Field of view (FOV) is defined as how much area a person can see with binoculars without moving them. Field of view is very important to consider when buying binoculars for hunting and other outdoor adventures.

Field of view requirement is different in different outdoor activities. For instance, you need a greater field of view for hunting but need a lesser field of view for birding or stargazing.

Relationship of magnification power and field of view:

The binocular with greater magnification power has less area to view, search or locate the target. Both are inversely proportional to each other.

Magnification ∝ 1/field of view

The relation given says that if you increase the magnification power then you will have to compromise the field of view of binoculars. This is why, we said earlier, always choose less magnification for hunting. During stalking, you need to locate. The greater field of view definitely helps in searching for the buck by providing a larger area.

Relation between magnification power and field of view

The image shows that the binoculars with less magnification give more area. It becomes easier to locate the target. In contrast, the binoculars with higher magnification power give less area to locate the targeted object. 

Binoculars with a greater field of view:

As said earlier, there are two possibilities. If you opt for a larger field of view, you will be able to cover a larger area. But if you find a target in that area, you won’t focus on that target. 

Binoculars with a short field of view:

Maybe you’re one of those who love a closer and fully focused look at the target. If yes! Go with binoculars with a shorter field of view. Choosing this type of binocular will reduce your area but increase the focus on the target.

What is the best FOV for a hunter?

New hunters don’t get it easy to find the target. Increased area of lookup will help them to find the target. Ultra-high focus on the target doesn’t help. The most important part of hunting is to find the target. If you fail to find the buck, the alone focus is useless. So binoculars with larger FOV are preferable over shorter FOV.

There are different fields to hunt on. For example 

  • Open area
  • Hunting in bushes
  • Hunting on mountain

If you’re hunting in any of the above fields, you must go with hunting binoculars with a wider field of view. Our recommended binoculars with the best FOV are listed below;

Carson VP Series with perfect FOV:

Number Explaining Exit Pupil Number

Exit pupil is another important point to discuss to give an in-depth answer to the question: What do the numbers on binoculars mean? Every binoculars have a small circle shape white-colored spot on the center of the eyepiece. This small circle is called the exit pupil which represents the size of the beam of light that leaves the eyepiece. It is measured in millimeters. Acknowledging the importance of the exit pupil helps in knowing how to understand binocular numbers.

How to calculate the exit pupil number?

The exit pupil size is calculated by dividing the diameter of the objective lens by the magnification power. Suppose the binocular with 10x magnification power and 50 mm objective lens diameter. Then the size of the exit pupil will be around 5 mm.


The formula to calculate the exit pupil is given below;

Exit pupil = Diameter of objective lens/ Magnification power.

The exit pupil of 10X50 binoculars will be calculated as follows

Exit pupil = 50/10 = 5 mm

Other examples are also given below;

  • Exit pupil of 10X42 binoculars is 4.2 mm
  • 8X42 binoculars has exit pupil of 5.25 mm
  • The exit pupil of 10X32 binoculars is 3.2 mm

 Ideal pupil number:

The exit pupil of around 5 mm is considered the best size. Anything above 2.5 mm falls under the decent exit pupil size category. If the binocular has an exit pupil of 2.5 mm or less than that, then never buy that binocular as it won’t give enough brighter and clearer images.

Number Explaining Close Focus

Close focus is simplified as the closest distance that can be focused with optical instruments like binoculars or scope. Smaller close focus helps in observing all the minute details of binoculars as it can focus the closer objects. It is especially important in bird-watching binoculars. 

Usually, binocular users don’t bother about close focus during purchasing the binoculars. After purchase, they use it to see the closer object and the binoculars fail to give a clear and magnified image of that object. The customers start abusing the sellers. 

In reality, each binocular has its own close focus, which means that each binocular has its own potential to focus on a nearby object. Suppose a binocular has a close focus of 2 feet it means it can only focus on an object which is 20 feet away from it. But it won’t focus on objects which are 19 feet away. 

For stargazing or sightseeing, the close focus of 30 feet is fine as long as you use binoculars far away from the targeted object. But in bird watching, you must have a close focus of at least 10 feet.

Type of Prism that a binocular uses:

Every binocular uses a prism to show the best picture. A prism is a triangular-shaped object that works or acts like a mirror. The incoming light through the objective lens strikes the prism and gets reflected. This reflection of light produces a sharp and well-oriented image. Two types of prisms are usually used in hunting binoculars.

• Porro prism 

• Rood prism

Porro prisms:

They were named after Italian scientist Ignazio Porro who discovered them in the 19th century. Porro prisms perform their function by collecting the light from the objective lens and passing it through pair of prism to get the magnified image. 

The Porro prism binoculars are zig-zag, enlarged in shape, and heavier. But unfortunately, these binoculars are very fragile. They get broken quite easily, so if you go on to buy that, be very careful.

Advantages of using binoculars with Porro prism:

Following are the benefits when you use Porro prism;

  • 3D and clear image
  • Wider field of view
  • Better image clarity

Roof prism:

Rood prism binoculars have a simple shape – two straight tubes that will show you the image. There are no complications in shape, but its working mechanism is very complicated. It consists of convoluted machined tubes (paths). The light passing through these convoluted paths gets reflected from the objective lens to the ocular lens.

Binoculars with roof prism provide higher magnification power than binos with Porro prism. More magnificent power means they provide a less or shorter field of view. Moreover, they are highly-priced, and newbies can’t afford to buy them.

Advantages of roof prism binoculars:

By using roof prism in your binoculars, you will avail following benefits.

  • More durability 
  • Lightweight
  • Good waterproofing
  • easy to carry in the hunting field

The best option to choose:

As roof prism binoculars are lightweight, durable, and come with better waterproofing, we recommend roof prism binoculars to use in the field. Not only we, but all the experienced hunters, use roof prism bino for hunting. So you should go with roof prism binoculars. Our favorite binocular with roof prism is given below;

Best Binoculars using roof prism:

Vortex Optics Viper HD Roof Prism - How to undertand the numbers on binoculars

The coating on the lens of binoculars:

All the lenses used in Hunting binoculars must be coated. The coating reduces the reflection of light on the glass of the lens to improve the quality of images that binoculars provide to the user. The lens without glass coating goes through the loss of light transmission from the objective lens to the ocular lens.

Light transmission drops to 65 to 70% if a binocular uses non-coated glass. In contrast, lenses with glass coating go through light transmission up to 95 to 98% from the objective to the ocular lens.

There are three types of coating available in binoculars.

  • Normal glass coating
  • Fully coating
  • Multi-coating

Only one optical objective gets coating at its surface in normal coating binoculars. All the glass surfaces and lenses used are coated in fully coated binoculars.  In multi-coating binoculars, the optical lens has multiple coated. At least one major lens has multiple strong coatings if not all lenses.

A coating of any type will be equally beneficial for you. The coating will enhance your hunting experience by providing high-quality images. Apart from that, the coating will protect your lens, enhance its performance and increase its durability.

Size of binoculars

The size of binoculars matters a lot if you aim to do hunting. Bigger-sized binoculars are merely a burden whereas compact optics are quite easy to carry in the field.

There are different sizes of binoculars present in the market. Some are very compact and others are bigger sized. The following picture gives an idea of the different sizes of binoculars.

The size of binoculars - What do numbers on binoculars mean
The size of binoculars – What do numbers on binoculars mean

Majorly three sizes are favored by binocular communities

  • Compact binoculars
  • Mid-size binoculars
  • Full-size binoculars

Choosing the right size is very important as the very small size binoculars may not give top-class image quality due to the lesser diameter of the objective lens. At the same time, full-size binoculars might have better image quality but they will be on a bulkier side due to the greater size of the objective lens. Make sure to choose binoculars that are smaller in size and vetter in giving quality images.

Which size of binoculars should a hunter buy?

Huntsmen spend a lot of time in the field. Sitting hours in the wait for a buck is common in the hunting field. So, your hunting bag should not be too heavy to carry. 

Suppose you choose a bigger-sized binocular and hang it around your neck with a strap. It will disturb you while prowling.

So, it is key to wisely choose and carry hunting gear with you during your hunt. 

Choosing a hunting binocular that is middle-sized, lightweight, and easy to carry must be a priority. Sometimes people make mistakes by buying expensive and top-class binoculars with the premium feature that are a heavy and more oversized size. So they get frustrated and disappointed in the hunting field.

Anything that destroys your hunting experience shouldn’t be a part of your hunting journey. Middle-range price binocular with decent quality and low weight makes it the best choice.

Focus Type:

Focus is very important in the hunting field. A good focus can make your day, and a bad one can ruin the whole hunting experience. It is usually said that.

”Hunting is all about eyeing”

But that’s doesn’t mean that you only focus with your naked and skip the focus type in binoculars. If you ignore the focus system, you might experience blurry images with faded spots. There are two focus systems available for binoculars

  • Centre Focus
  • Individual Focus

Centre Focus system:

Most of the hunting binoculars use a center focus system. This system consists of a round-shaped knob or small wheel that can be rotated to adjust the focus. This knob can be accessed through the index finger as it is present in the middle of two barrels of binoculars. This system also consists of an adjustable eyepiece. 

By moving the small knob or wheel, you can change the focus of both eyes. Centre focus system is not recommended if you use your binos in the evening or a low light place. 

Individual Focus system:

The individual Focus system consists of two small wheels for two eyes. The unique focus of both eyes can be set. 

The good thing is that those binoculars that use an individual Focus system can be used in low-light areas. For example, the military corps uses these binoculars to go on low-light missions. 

Water-resistance is another significant feature that attracts most people. It’s is a low-budget product as compared to central-focused type binoculars.  

Focus is key in hunting. Never underestimate the value of focus type. Choose the best focus type that suits your hunting method and budget.

Vanguard VEO ED 8×42 binocular:

Vanguard VEO ED 8x42 binocular for hunting

Video ability of binoculars:

Video ability of binoculars is a luxury, not a need. Most of the hunters, especially new ones, have limited resources. They try to buy the best hunting binos on a limited budget. So, the budget binoculars won’t come with the luxury of video ability. 

But those who are experienced campaigners and are looking to upgrade their binos and hunting experience should use choose binoculars with a built-in camera. 

Being a hunter, I know how beautiful moments I come across while stalking. I love sharing my own hunting stories and moments with my family and friends. I feel the same for you.  The built-in camera in binoculars can record videos and capture pictures with high quality. You can capture the moments and share them with your buddies. 

Have you ever faced the problem that your mobile’s battery gets drained out? Well, that’s a regular practice to me. Even if your cell phone is switched off, you can still have a great option of making videos and capturing the natural beauty while hunting.

Built-in cameras have different types. It depends on your needs. But we recommend you use a camera that has higher battery timing.

Vazussk 2″ HD Digital Binocular:

Vazussk 2" HD Digital Binoculars - How to choose binoculars

Video explaining what do the numbers on binoculars mean


In this article on how to read binocular numbers, all the important numbers and specifications have been explained completely. After reading this, you will be able to go to the optical store and buy a nice pair of binoculars on your own. Keep in mind one wrong decision at any step can bring you unsuitable binoculars for you. 

Remember that high pricing doesn’t mean very good binoculars. Similarly, low-priced binoculars are not always bad. Don’t go for the cheapest binoculars as you won’t get any results at all. A mid-range binocular can perform very well in the field.

“Never rush for expensive, nor for too cheap.”

We have listed all those factors. In fact, every factor is explained to help you understand the numbers written on binoculars binoculars