Sizing A Muzzle With Another Muzzle
Another method of sizing a muzzle for your dog is using their old muzzle. This obviously cannot help you if you have not used a muzzle on the dog before. MTT have made it much easier to do this method since we have measured almost every brand and size out there.
You can use the measurements of the muzzle and also the comparison charts (in Accurate Muzzle Charts) to work out your dogs rough closed or even open measurements.
For example if the Baskerville ultra 6 was too long but a good height and width for your dog, you can assume measured length should be under 4" since the 6 is 4" length. The width would also be approximately 3" and front height is 4.75". Which means you can find a muzzle that is the same as Baskerville 6 but slightly less length.
First photo (four pictures)
Top Left: Dog wearing a Baskerville 5 that is too small for full pant, from this I can tell the dogs length is just over the Baskervilles length (3.75"), and the height fits a regular pant but not a full, the size 5 front height is 4", so I gave two sizes, one that was 4" length and similar width but 1.5" more height than the 5, and a size that was similar but 2.5" more height. The owner went with 2.5" more height to ensure it was enough room and the muzzle in top right is the new muzzle.
Bottom Left: Dog is also wearing a size 5 Baskerville, owner stated they liked the fit but it was slightly long, so I found sizes of similar height and width but with less length which fit the dog perfectly. Just an example on how you can size without measurements fairly easily.
The second photo
First picture shows the dog panting in the Baskerville size 4 which we know is 3.25" length, 2.5" front width and 3.5" front height, we can see comparing to the full pant out of the muzzle that the dog needs a bit more room to properly fit pant. You can also see length looks good and you would need to find something around 3.25-3.5" length. Width you cannot tell from this side which is why you would need more pictures.
The third photo
These two pictures show a size 6 Baskerville that is clearly too small for this large dog, we can see its length is a quite a bit less than the 4" length of the 6 but not half of it so you could put length around 2.25" OR you could actually measure the muzzle (off the dog) to get a closer measurement. You can also see the width is too snug so the dogs width is approximately 4" since that's what the size 6 is. We can also see its pant is restricted but without seeing the full pant it's hard to tell how much by, you can confirm with a full pant pic or you can use the approximating method to add some height.
