It really depends. I know thats the typical answer to a lot of questions here, but if you're medically sound (no major health issues) you could be out by noon, but if there are 40 or 50 people doing it with you that day, you could still get stuck until 3:30 or so, if you have medical issues you may have to wait for certain things to get cleared. I was completed by 11:30 (went in at 0500 and was with a group of 25 or so), went down and had my free turkey sandwich, coke and an apple, then had to wait 2 hours just to get finger printed. Side note, the finger printing was kinda cool, I had never been before and expected to be covered in ink, but it was all digital, haha technology eh?! Long story short, plan that day just for MEPS, if you get out early take it as a sign to relax, if you get stuck, welcome to the DoD.