Gordon26 says on 16/Aug/11
Met Johnny at a Pizza Hut (in Long Beach,CA) counter 'bout a week ago. He was wearing regular 0.75 inch thick skater-sneakers - same as me. It was around noon. I'm 6'0.75 and Johnny was a-shade shorter than me. I'd say 6'0.25 (183.5 cm) at best, he had a great posture. We were almost on an eye-level. I was there with my buddy who's 6'2 and he looked clearly taller than Johnny. He was looking directly at his forehead.
So I'd say he's 6'1.5 in the morning at best and 6'0.25 midday.
Definitely a tall guy 6'+ group.

Tommie says on 20/Jun/11
next to 6´3 Tony Hawk .. that looks really strange.
Click Here

on another picture you can see that Knoxville is wearing his chucks (what a surpise) Toyn is wearing some skate shoes

search it on google images: Johnny Knoxville, Tony Hawk

Dan says on 8/Jun/11
in dukes of hazzard, him and sean william scott both have boots on right?, he looks maybe an inch taller, i think 6foot on the dot

Mohammed says on 26/May/11
I would say he's 182-183 cm, doubt he's 184 let alone 185.

Silence DoGoode says on 30/Apr/11
I work for a major airline. Johnny has been to my counter, he stands 6ft tall, (same as I) and while I checked him in, he was standing on the bagscale. Wearing jeans, sneakers and a t-shirt, he was 184 pounds as of 2-2011

somebody new says on 13/Mar/11
howard stern asked him about his height and weight and he said 6-1, 178ish (170 while filming jackass)

SAK says on 5/Feb/11
Just watching jackass2 right now and looks 184cm/6ft0.5. He is slighter shorter then Will Smith(187cm/6ft1.5).

Rampage(\\-_-_-/)Clover says on 27/Oct/10
6"0 flat or 183cm is nearer. He was about 2 inches shorter than Will Smith in Men in Black 2.