Length, Width, Height
Length, width and height are the most important things to look at when fitting a muzzle, though this can be hard to do when companies don't even give these measurements to size with which is why we went and fully measured hundreds of sizes.
Length Of The Muzzle
Length is a tricky one to fit, as what works for one dog may be different to the next. In general the muzzle should sit 0.5" away from the eyes and 0.25" off the nose. This will stop the muzzle being pushed into the eyes without being short enough that they could pull it over the end of the nose.
For example if the dogs length is 4" from the tip of the nose to 0.5" away from the eyes, you would try find a muzzle that is as close to 4.25" as possible to allow for the space needed to stop it touching the tip of the nose. Because this is not possible for everyone due to limited sizes due to availability or even pant size (if your dog has a bigger than average pant you will find the muzzles get long, the taller they get on most brands, so this is where you may need to sacrifice a 'perfect fit' on length to make sure height fits (more info in the tabs above).
A lot of dogs can go shorter or longer than this recommendation and do absolutely fine in their muzzle. Though we do not recommend more than 0.5" long for small dogs, 0.75" for medium and 1" for large, though this is very general and hard to accurately give an exact measurement as it depends on many things, which is why we recommend using MTT Program to send in your info so we can do the hard work for you.
Another issue with making sure length works is the chin length of the muzzle, if it is unusually long or even if you have to modify the muzzles length right down, because in most cases the chin cannot be modified unless something like a JAFCO, you may have issues getting the length to fit correctly if the chin is pressed against the neck. When this happens the muzzle will likely push up off the nose and won't go any shorter, even though by length measurements it should have it correctly.
An example is the Chopo 20C, is 4.25" length including the noseband, when modified down it goes to 3.5" length, BUT its chin length is 5", so you can see if your dog has a 3.5" length, this muzzle could fit but the chin may end up stopping the muzzle from being shortened. This explained much more in fit issues above since it is difficult to judge chin length without trying the muzzle on first.
0.5in/1.3cm
0.25in/0.65cm
Width Of The Muzzle
Width is a more relaxed measurements since most dogs do fine with a bit more than needed, plus most muzzles can have their width modified to fit the dog better. However whilst extra width may work fine, a muzzle that is too narrow won't work and can restrict the dogs pant and cause rubbing.
The muzzle should sit comfortably over the nose, whilst also allowing the dog to pant, since usually their pants will be wider than closed mouth too. over the snout the dog should have approximately 0.5" - 1.5"of room depending on it's size and pant.
There is the front and back width of muzzle, most muzzles will have a bigger back width than front. If you only see 'width' it is likely back width. Most back widths can be squished down to the muzzles front width or widened if needed too.
One issue with muzzle widths is the cheek bars, some dogs have much wider heads/cheeks than their snout, this can cause the cheeks to be too tight, but most of the time you can still widen these as well.
Another thing to note is back width of the muzzle is taken in the same spot as your dogs width. The back width is not back near where the straps attach as the cheeks can come wide or narrow depending on how they were handmade/stored, we sometimes refer to this as the cheek width. A muzzles front width should be similar or slightly less than your dogs width.
Front Width: Top Orange Line, Not Modifiable
Back Width (or just Width): Middle Blue Line, Modifiable
Cheek Width: Bottom White Line, Modifiable
Height Of The Muzzle
The height of your muzzle will depend on your dog and it's pant size. You may either need a muzzle for your dogs full pant or their regular pant and depending on this will decide how well the height of the muzzle fits the dog. If your dog has a small pant and the muzzle looks big, then its likely too much height. If the muzzle seems big but you know the dog has a large pant, then you need to get them panting in it to accurately judge the fit.
Height should never be less than their regular pant, for any reason a muzzle that also restricts a regular pant is unsafe. It also should not be overly big either, if you have a small dog height shouldn't be more than 0.5" taller than their pant, medium dogs around 0.75" and larger can be fine with up to 1.25" more height, though we don't usually recommend over 1" unless there is no other options that will fit better.
Depending on the dog their chin can also touch the muzzle whilst panting and it is completely fine for the dog, other dogs may need some extra room if it starts rubbing or if you see them panting larger quite often.
When you see the dog panting in the muzzle, you should be able to instantly tell whether or not the dog is restricted or if the muzzle is way too big as there will be no space or a large amount of space not used. The muzzle should a close to perfectly fit your dogs pant, this wont always be the case with slightly big muzzles that are not possible to be sized down.
In the photo you see a dog at closed mouth in and out of the muzzle, you can see why to most this muzzle may look big (especially compared to the tiny ones people recommend), but as the dog goes to a regular pant you can also see that much more room has been used. If the dogs pant wasn't to get bigger than the regular pant size then yes this muzzle would be too tall, but as you can see when the dog is fully panting, she takes up almost all the room in the muzzle, thus making this a well fit muzzle. It is slightly tall but still works great since the size down would not fit based on how much room this dog takes in the muzzle.
Need A Pant To Confirm Fit
Comparing a photo of your dogs full or regular pant to them wearing the muzzle is the only way of properly judging the height/pant room. The muzzle can look unusually big or small but without seeing the dogs full pant in our out of the muzzle there's no way to tell if it fits or not. If its obviously the wrong fit and too small/big then you will know but in general telling someone their muzzle doesn't have enough pant room without seeing the dogs pant is far from helpful. Some dogs have tiny pants so the muzzle may look small and others may have huge pants and the muzzle may look massive when the dog isn't panting.
Some people may also only need the muzzle for their dogs regular pant making it look smaller than what is needed for exercise too.
