From United Airlines Website - 9 inches x 14 inches x 22 inches @ ? lbs.
From Air Canada Website - 9 in x 15.5 in x 21.5 in @ 22lbs
That being said, I have never had anyone question my carry on, weigh it, or size it, both domestic, and intl. Fly maybe 1/month
As long as it makes it in the overhead, you're good IMO, although I'd be careful with it flying with someone who gate checks United Express Jet always does for me on the short hauls. No way I'm checking a nice bag like these ones, easy way to put 5 years extra wear on it in 2 hrs.