Muzzle Energy Computer

Bullet Weight (grains): (grams): (ounces):
Velocity (feet/second): (m/s):
Bullet diameter (inches): (mm): (gauge):
Energy (foot pounds): (joules):
Efficacy (energy x area): Sec. Dens.: E*SD:

The top three rows above are active. Change any number and everything dependent on it will be recomputed.

Efficacy is a measure proposed by L. Neil Smith. It is defined as energy in foot pounds multiplied by projectile cross-sectional area in square inches. Neil says that this is a pretty good indicator of the relative efficacy against live targets of different projectiles and loads. In an email about this page, Neil wrote, "I'm not absolutely certain of its applicability to rifles (although it looks pretty good and is fine for slugs and rifles like .45/70). There are other factors at work above 2000-2500 feet per second. But every year that passes convinces me more that this is the perfect program for predicting handgun performance."

Sectional Density ("Sec. Dens." above) is defined as the weight (w) of the bullet in pounds divided by the square of its diameter (d) in inches: w/d^2 = pounds per square inch.

Muzzle Energy for Palm is a Palm handheld organizer version of a subset of this page's functionality.
iPhone Muzzle Energy Computer is a version of this page formatted to fit on the screen of Apple's iPhone.

Copyright 2006 Bill St. Clair
Copying and reposting allowed as long as this copyright remains intact

Tip o'the hat to Bob Mier