You can calculate something that John Taylor created, with this page. Taylor was a big African game hunter of the mid-20th century and he had experience with what stops huge game like tigers, lions, elephants and hippos. He came up with a pretty simple formula for what he called, “Knock Out Power.”

This formula is simple. You take the weight of the bullet (in grains), times the speed (in feet per second), times the diameter (in inches – like .451) and after multliplying the results, you divide by 7000 to give you a reasonable number to work with, somewhere between 1 and 100. Perhaps he used 7000 because that’s how many grains makes a pound, but in any event it gives a workable number. ( TKOF = weight * speed * diameter / 7000 )

This formula is biased towards the bigger and heavier bullets, but that’s what he wanted to have a scale to Knock Out big game. Plug in some light 30-06 loads and compare to some 500 S&W loads with a very heavy bullet for comparisons. Example: A 30 caliber 150 grain bullet moving at 3,000 fps = 19.3, while a 50 caliber, 630 grain bullet moving at 1300 fps = 58.5 a huge difference, but for Taylor, he felt that’s what would take down big game best. If you want to save your data, print this page after you make a calculation.

Weight of Bullet (grains) Bullet Velocity (feet/sec)
Bullet diameter (inches) Taylor KO Factor