Bullet Energy Calculator

Bullet Kinetic Energy

Muzzle energy quantifies how much kinetic energy a bullet carries when it leaves the barrel. Ballistics charts often list mass in grains and velocity in feet per second (fps).

Energy Formula

$$KE = \frac{1}{2} m v^2$$

With mass in grains and velocity in fps, convert to SI units first: one grain equals 64.79891 mg, and one fps equals 0.3048 m/s. Energy in joules converts to foot-pounds force by dividing by 1.356.

Typical Values

A 150-grain bullet at 2800 fps carries about 2600 ft·lbf (3500 J). Heavier or faster loads increase energy proportionally to mass and with the square of velocity.

Frequently Asked Questions

What is a grain in bullet weight?

A grain is 1/7000 of a pound, or 64.79891 milligrams. Bullet weights in the United States are commonly listed in grains.

Why does velocity matter more than mass?

Kinetic energy depends on $v^2$ but only linearly on mass. Doubling velocity quadruples energy; doubling mass only doubles it.

What is the difference between ft·lbf and joules?

Both measure energy. One foot-pound force equals about 1.356 joules. Hunting and sporting literature often use ft·lbf.

Is muzzle energy the same as downrange energy?

No. Drag and gravity reduce velocity in flight, so energy drops with distance. This calculator gives muzzle energy only.

How do I convert grains and fps directly to ft·lbf?

A common shortcut is $E = (m_{\text{grains}} \times v_{\text{fps}}^2) / 450240$, equivalent to the SI calculation used here.

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Bullet Kinetic Energy

Energy Formula

Typical Values

Frequently Asked Questions

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