Bullet Energy Calculator
Muzzle energy measures the kinetic energy of a bullet as it leaves the barrel. A 147-grain 9mm bullet at 990 fps produces about 320 ft-lbs of energy, while a 230-grain .45 ACP at 830 fps produces about 352 ft-lbs. This calculator also computes the Taylor Knockout Factor, which accounts for bullet diameter as a rough stopping power comparison.
The muzzle energy formula in imperial units is:
KE = (bullet weight in grains * velocity in fps2) / 450,240
The constant 450,240 comes from 2 * 7,000 (grains per pound) * 32.174 (gravitational acceleration in ft/s2). This gives the result in foot-pounds.
**Taylor Knockout Factor:**TKO = (weight in grains * velocity in fps * bullet diameter in inches) / 7,000
Developed by big game hunter John "Pondoro" Taylor, TKO accounts for bullet diameter as a factor in stopping power. For comparison:
- 9mm (147gr @ 990fps): ~320 ft-lbs, TKO ~7.4
- .45 ACP (230gr @ 830fps): ~352 ft-lbs, TKO ~12.3
- .308 Win (168gr @ 2,650fps): ~2,620 ft-lbs, TKO ~19.3
- .375 H&H (300gr @ 2,530fps): ~4,263 ft-lbs, TKO ~40.5
Competition shooters use power factor (bullet weight * velocity / 1,000) to classify loads. USPSA Major is 165+, Minor is 125+.