measuring punching power

I see knockout power being a combination of technique and placement rather than brute strength.

In boxing and MMA, they always teach to try and either avoid a punch or, if you have to take it, take it off the top of your skull (like from the forehead up). The density of the skull and absorb and cushion the brain from most attacks (to a degree). The same thing with the sinus cavities and cheekbones- they're designed to absorb and protect. The mandible, or the jawline, as solid as it is, it's loosely connected to the rest of the head. Being a moving joint, it has the ability to transfer power better than a fixed surface (like the skull). Remember when Anderson Silva dropped Forrest Griffin? That jab he threw couldn't have been more than 50% power. But it landed square on Griffins chin, which transferred the power to his cerebral cortex, and caused him to lose his faculties.

Sort of a metaphor, imagine kicking in a metal door. You can bang away with all your strength in the middle of the door, and you may cause some damage, but you won't get the door open. Now if you place a good kick right at the point where the door latches with the wall, 9 times out of 10 you will swing that bad harry wide open like an action hero. So, in short, Its not so much power as it is placement. Train on a bag using a little colored dot about chin height, and have your punches land there.