How to Calculate Bullet Impact With Energy

Calculating the energy of a bullet is a straightforward process.

The energy of a bullet is a function of its mass and velocity. The formula for the energy of a moving object is one half mass times the velocity squared. Typically, energy units in the International System of Units are expressed as joules. This is expressed as kilograms per meters squared divided by seconds squared. However, most hunters or shooting enthusiasts prefer to deal with the energy of a bullet in foot-pounds. Although it is possible to convert foot-pounds directly from joules, the typical information provided for a commercial cartridge provides the data for a foot-pound calculation.

Things You'll Need

• Calculator

Instructions

1. Determine the mass of the bullet in grains. This is typically printed on the box of commercially available cartridges. If not, contact the manufacturer or retail supplier for this information.

2. Determine the muzzle velocity of a fired bullet. The muzzle velocity is typically printed on the box of commercially available cartridges and is given in feet per second (fps). If not, contact the manufacturer or retail supplier for this information.

3. Apply the following formula to that information: ((Mass in grains) X (Muzzle velocity)^2)/450400.

4. Obtain the value in foot-pounds using the above calculation. The constant 450400 takes into account the proper unit conversions and the half mass in order to get the energy balanced correctly. If desired, conversions can then be made to other energy values, such as joules or ergs, by applying standard conversion values.

Tips & Warnings

• If joules are initially desired because the information is already provided in the metric system, the bullet weight must be known in grams and the muzzle velocity in meters per second. Then use the formula: (0.5(mass X velocity^2))/1000.

References

• Ask a Scientist: Momentum and Kinetic Energy
• M.D. Smith's Reloading Pages: Foot Pound Calculations