I agree - if in my area, would be at least 4 yrs. But, if this is a Kansas Deer, they are as big at 2 as ours are at 4 - so a little difficult for me to tell. He would be a shooter here.
His head suggests older than 4, but once a buck is mature it is pure guess work on their exact age unless you know him from younger years. All that said wouldn't surprise me if he's not 6 (+)