What size frame of mountain bike?

Definitely try various sizes to see what fits, ideally working with shop folks who know what they're doing. You'll want to explain your plans for riding (what types of trails, how aggressive, etc) and you'll want to consider torso and arm measurements, in addition to inseam and height. Ultimately, you just need to be comfortable and not sitting so low that you hurt your knees pedaling, nor so high that you feel off balance, can't move the bike enough beneath you and/or can't jump down without hitting the top tube (OUCH). I'm not giving you a size here because your height alone can't determine it. For example, I am 6'1" and ride some medium/18" and some large/19-20" frames because my inseam is only about 31". How much leg and how much torso you have will make a lot of difference. There are people my height (and probably shorter) who properly fit larger frames. Finally, frame size varies a great deal among brands, and there's little to no consistency in how measurements are taken or what "small", "medium" and "large" mean. Ideally, a seat tube measurement (most common size indicator) should be taken from the center of the bottom bracket (crank bolt) to the center of top tube on a bike with a level top tube and not too much seat tube above the top tube. Most MTBs have sloping top tubes now, however; so it's not simple to measure these things. Here's a great site with sizing and lots of other bike info: http://www.sheldonbrown.com/frame-sizing.html

Go to your LBS and they will hook you up. Otherwise no one can tell you for sure what size bike you would need.

It depends on your inseam measurements. 20in should suffice.

Large 19 or 20 inches But depends on leg length not overall height. Mountain bikes are less critical than road bikes since they have much more adjustment in seat height and position and handle bar height. Good luck, Happy cycling

It would be a Large frame. Based on your pant inseam (typical is 29-30") you would need a Large frame with a 175mm crank arm length. If your legs are longer or shorter than the typical person who is 5'11" then you should go with wither a longer or shorter crank arm length. Hope this is helpfull