At the left of the picture, the tape ends at 3″.
It appears the tail probably ends at 2″.
At the right of the picture, the mouth is open and it appears to be sitting between 23.5″ to 24″.
Close the mouth, you are probably sitting at 23″ (proper way to measure smallmouth)
Best bet that I can tell, by looking at the picture, is that the fish is 21″.
NICE FISH!!!!
Also, doing some other views, it appears that the fish is 7″ top to bottom.
Guessing it might be 2″ wide atleast, probably 3″ wide, you are looking at a 18-20″ girth.
a 21″ fish with an 18″ girth will average mid 6lb range.
Again, beauty of a fish!
CONGRATS!!!!!
You have a good pic, I would look at getting a replica of that baby!