Foot-Pounds
Also: ft-lbs · ft·lbf
Standard US unit of kinetic energy at the muzzle (or any specified distance). Computed from bullet weight and velocity.
The formula is ft-lbs = (grains × fps²) / 450,400. A 140 gr 6.5 Creedmoor bullet at 2,800 fps carries roughly 2,438 ft-lbs at the muzzle. By 1,000 yards it’s down to about 1,000 ft-lbs.
Different hunting cartridges have rough energy thresholds for ethical kills on various species (the 1,000 ft-lbs minimum for whitetail at impact is the commonly cited rule). For precision rifle competition, energy matters less than retained velocity above transonic.