What Do The Two Numbers On A Binoculars Mean? All Explained

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Updated on: 

October 12, 2021

Our Fool Proof Guide To The Numbers On Binoculars

For first-time buyers of binoculars, the numbers can be a little confusing if you are looking for high-quality binoculars. 

The two numbers on a pair of binoculars refer to the magnification power and objective lens size of your powered binoculars, the greater the first number, the further you can see images, the higher the second number, the more light your binos allow for a brighter image.

As finding your pair of binoculars can be a little overwhelming, we have explained in more depth how these numbers work below and what number you should be looking for on your binos, we will also discuss the other numbers on binoculars and what they mean too. 

What Does The Magnification Number Mean? 

The first figure on your binoculars with the 'X' sign is your magnification, on most regular binoculars this will be between 8x and 10x but for expensive binoculars they can have an extreme sized zoom binocular size of 12x or even 15x. 

This would mean that types of binoculars with an 8x magnification would make objects appear 8x closer and so on. 

Depending on what you need your zoom binoculars for will determine the size of the magnification, we have listed some common magnification sizes according to the activity below. 

  • Theatres and concerts - For concert venues, you need a pair of binoculars that are compact and easy to carry with a large enough angular view for seeing the whole stage, therefore we would recommend any binos with a magnification of under 8x.
  • Bird watching & hunting - When birdwatching, you want to ensure that your binos have a wider field of view for tracking moving subjects, therefore your magnification level should be around 8x.
  • Hiking or travelling - In terms of hiking or travelling, binoculars with a 10x magnification level will be a versatile binocular and not too heavy.
  • Astronomy - For astronomy, your binoculars must have a high strength of magnification if you want to see planets and stars, this would be 15x or even 20x.

You should always remember that a higher magnification number does not always mean better binocular lenses, sometimes a larger magnification level will mean a lower angular field of view and would require stabilisation such as a tripod. 

What Does The Objective Lens Size Number Mean? 

The second number on your binoculars will usually be stated in mm and refers to your binoculars objective lenses size or aperture controlling light conditions in your image. 

If you go for binoculars with larger lenses, they will allow more light in and will be more suitable for use for astronomy or in low-light conditions. For example, a 12x50 binocular has 12x levels of magnification and a 50mm aperture. 

It is important to remember that wider lenses with more light are not always the better option and can make your pair of binos very heavy.

Other Binocular Numbers Explained 

Now we know what the main two binocular numbers mean we can get into looking at the other numbers which will be stated on your binos specs so as you can understand everything you need to be looking for in your new binoculars.

Field Of View 

The field of view on your binoculars is typically expressed per 1000 yards, it is a very important number as it determines a decent field of view through the lens which is essential in activities such as sport if you want to track moving subjects. 

Anything with a FOV of over 300ft is excellent, remember that this number will be limited if you have binos with a higher magnification. 

You may also see an angular field of view on your binos expressed in degrees, this refers to the same number as a field of view, any binocular with a 6-degree angular field of view and above is a good choice. 

Eye Relief 

For people who wear glasses, you must ensure that you look at the eye relief number on your binos before buying. Binoculars that have a small eye relief will cut off the image that eyeglass wearers see when looking through the lens, so the number should always be bigger in this case. 

Always look for an eye relief of over 15mm relief for eyeglass wearers.

Exit Pupil

Another number you will see on your binos is the exit pupil, this number refers to the light beam which comes out from each eyepiece and is typically measured in mm. 

This number becomes important if you are planning to use your binos in low light situations, as a larger exit pupil will provide you with the clearest images. 

On most binoculars, the exit pupil will be around 4-5mm, but if you can get higher up to 7mm this will be excellent for producing sharper images. 

Close focus 

Lastly, we have the close focus number, this number refers to the minimum distances that you can focus on something, anything around 2m is great, but it can be hard to find a low close focus distance on cheaper binos for the perfect focus. 

How To Set Up Binoculars

Figuring out the numbers for binoculars can be a little overwhelming as a first time binocular buyer but so can setting up your binos, with you having to adjust the dioptre and focusing ring.

We have put together a simply follow step by step guide below that will cover how to set your binos for the first time. 

  • Step one - First of all adjust the eyecups on your binos, twist them up fully if you do not wear glasses or set them at their lowest position if you do wear glasses for a better field of view.
  • Step two - Adjust the eye width of the bino barrels until you can no longer see black rings overlapping.
  • Step three - Take your binoculars and try to look at a subject at least 50 metres away, close your right eye then adjust the focusing ring until the image in your left eye is not blurry anymore. Then close your left eye and adjust the dioptre ring till the image in your right eye is not blurry too.

Frequently Asked Questions About Numbers & Binoculars 

What are roof prism binoculars? 

Roof prism binoculars have a more complicated internal system than Porro prism binos when it comes to the light, this often makes them more expensive but also compact and lightweight, making them a better investment if you want a pair of small binos that produce high-quality images.

Which objective lens size should I buy? 

The objective lens size of your binos by standard should be over 20mm and under 50mm for average use, this will ensure there is enough light in your image but will keep your binos a reasonable weight too.

Are lens coatings important? 

Yes, lens coatings are very important on your binos as they improve image quality and stop reflection as well as colour fringing.

How do I know which binos to buy? 

You should choose your binos according to what you will be using them for, for example, for hunting, you would choose 10x binoculars with a 42mm objective lens, lens coatings, waterproofing and a decent field of view.

What does the close focus number mean?

In some situations you may want to zoom in on a subject that is a little closer to you, the distance refers to how close this subject can be until your binoculars cannot focus on it anymore. Close focus is great when birding or hunting.

Is a higher magnification better? 

No, a high magnification does not equal a better pair of binos it simply means you can view subjects from further away, you will have to have binos with built-in stabilisation to stop the shakiness or a tripod when using highly magnified binos.

What are 12x binoculars good for? 

Some 12x binoculars would be excellent for long-range spotting or astronomy purposes when viewing basic stars and planets. We would not recommend them for bird watching or sporting events however as they would have a more limited field of view and a little blur when handheld.

Final Words 

Overall, the two numbers on binoculars refer to the magnification level and objective lens size that your binoculars have. It's best to choose a magnification according to the activity you will be using your binos for, and for the objective lens focus on how much you will be using your binos in low light. 

Always have an idea of the binocular numbers you want on your model before researching so as you can narrow down the most suitable models with ease for your purpose of use. 


Born and raised in the south coast of UK, a small town close to Cornwall, I have adventure in my blood. Ever since a young age, I have always been into the great outdoors and particularly love watching the natural wildlife. Birdwatching is what I enjoy the most, and thus my natural interest in binoculars began. I founded and run Best-Binoculars.UK a site where I talk about various aspects of and review binoculars. Hope you enjoy my ramblings :)

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Born and raised in the south coast of UK, a small town close to Cornwall, I have adventure in my blood. Ever since a young age, I have always been into the great outdoors and particularly love watching the natural wildlife. Birdwatching is what I enjoy the most, and thus my natural interest in binoculars began. I founded and run Best-Binoculars.UK a site where I talk about various aspects of and review binoculars. Hope you enjoy my ramblings :)

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