JnR Photography
Written By:

How To Measure Camera Lens Size

Published On:
July 23, 2021
Items purchased through links help us. By doing so, we make a small commission at no extra cost to you. Learn More.
If you're looking for a quick and easy way to measure camera lens size, then read on! This is an important part of photography that many people don't think about when they are buying a new lens, filters, or other equipment. Our article will teach you exactly how to measure camera lens size.

By the end of this article you won't have to wonder what your camera lens size is - and you'll be able to make all of your purchases with confidence going forward!

Let's get to it!

Don't Mistake The Diameter Of Your Lens For The Focal Length​

The easiest way to identify a lens is by it's focal length.

Some common focal lengths are 24mm, 50mm, 85mm, etc. You get the idea.

Some beginner photographers mistake this for the diameter of the lens. They then get confused because when they're looking for equipment for their lens (like a filter) - they can't find a 50mm filter.

If this is you - don't feel bad. We've all been there.


An 85mm lens is a lens with an 85mm focal length. Technically, it's the distance from the sensor to the point of convergence - or the point where all light that passes through the lens converges and then passes to the sensor, together.

A basic explanation is how wide or narrow your field of view is. A lower focal length value (like 24mm) is much wider than a higher value (like 100mm). Makes sense, right?

That's focal length in a nutshell - don't confuse this with camera lens size or diameter.

**Also, be aware that lenses of the same have different sizes. This can be because of different manufacturers or different apertures.**

**The images above show the size difference between an F/1.8 and an F/1.2.  Overall the GM (second image) is much larger, this includes the diameter.**

Diameter Of Your Lens​

The moment you pull the trigger on a new lens - your creative side is thriving, almost overstimulated. You're imagining all of the amazing photos you'll be able to take with it.

One thing that is overlooked by most - is the diameter of the lens.

While it usually isn't a big deal, there are things that are affected by the diameter. These include:

  • Size and price of filters
  • The ability to actually use a filter

The Diameter Of Your Lens Determines The Size Of The Threaded Filter​

That's right. The diameter of your lens determines the threaded filter size. Generally speaking, the larger the diameter - the more expensive the filter will be. Larger filters can be harder to find as well.

I've included a comparison chart below. It shows how larger filters are more expensive than smaller ones - and they're sometimes out of stock for months while smaller filters continue to be in stock.

Lenses That Require More Gear​

Believe it or not - there are lenses on the market that don't allow traditional hardware or filters.

Wide angle lenses are a common one. Generally speaking, anything below 24mm require a special mount and filter. This is due to the curvature of the outer glass (pop out bubble). There's a special mount that attaches to the lens and a filter slides through and is held by the mount.

Another instance would be if the front element is just too big to accept filters/mounting. A good example would be the Canon 200mm F/1.8 or a 400mm F/2.8. The front elements are too large to accept threaded filters (and if they did, they would be huge and incredibly expensive).

Measuring The Diameter Of Your Lens​

You can do this by measuring it with a ruler or tape. This is a super old school way of doing it - but, you'll ultimately know the diameter of your lens.

You do this by taking a ruler or tape and while looking at the front element - measure from the very outer edge of your lens (where the threads are), to the other. Do this while passing over the center of the front element.

Passing through the center is critical, seeing as if you 'cheat' the measurement (not quite through the center) - your measurement will be off.

Write down what you got, and double check. Once you're confident with what you got, that's the diameter of your lens threads - and the diameter of any threaded filter you want to put on it.

There Is A Much, Much, Easier Way...​

Once I tell you this, you may wonder why I even went into talking about the tape/ruler measuring... Well, I want to give you options. There could also be an instance where you aren't able to use the method that I'm about to mention.

The easiest way is to read the numbers that are on 90% of all lenses, around the inner glass/threads.

This number next to the symbol if your lens/thread diameter.

Easy right!! Very.

Now, I mentioned the method from before because this writing can wear off. It's basically painted on the lens - this can wear off. If you buy a second hand lens that's worn and you can't read it, you now have a method to find it yourself.

Now, What Can You Do With This Information?​

The most common reason for needing to know this information is for lens filters. Here is a list of filters that benefit various types of photography and video. I'll then break that down and divide them into either photography or videography filters.

Most Common Lens Filters:

*The examples below are amazon links.  We are currently working to flesh out this article and add content on each individual filter*  The Best Variable ND Filter is our latest article towards getting all of these filter types explained.*

Common Lens Filters For Photography

Common Lens Filters For Videography

The rest of the filters are very specific and are only used for one type of photo or video (like astro or infrared).

*Lens diameter is information you'd need to know for lens caps too.*

That's It! You Know How To Measure Camera Lens Size!​

As simple as this article may seem to some, sometimes it's the most simple of things that people either forget or have a hard time grasping.

Don't fret! You now know how to measure camera lens size, both the old school way (with a ruler) and the much easier way (written on the lens itself).

You can now get all the filters and 'extras' that you need with confidence knowing that you know the correct diameter!

If you'd like to follow us, we're on Facebook, Instagram, and Pinterest.

You can also learn a little more about who we are and why we do what we do, here.

We hope you learned a thing or two here today - leave questions and feedback below! We love hearing from you all!

Until next time, take it easy and keep creating!


What do the numbers mean on my lens?

We talk about this topic in more depth in our article - but there are two forms of 'measurement' for a lens. One is its focal length (the number you see on every lens IE 50mm, 85mm). The second is the thread or filter size. This number is found on the front element of your lens (in writing) - it's the number you use for both filters and lens caps.

What size is my lens filter?

This would be determined entire by the manufacturer and the f/stop (aperture) of the lens. This is because, each manufacturer's size (in general) of their 50mm may vary - and lower f/stop lenses have larger front elements. Meaning, an F/1.8 50mm lens will have a smaller front element than a 50mm f/1.2 (49mm vs 72mm, respectively).
menu-circlecross-circle linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram