FPE calculator — Foot-pounds of Energy
Calculate projectile energy based on provided mass and velocity. FPE calculator — Foot-pounds of Energy supports shooters, hunters, engineers, and educators evaluating projectile performance.
Highlights
- Calculate projectile energy in foot-pounds from mass and velocity.
- Supports grains, grams, kilograms, ounces, and pounds.
- Convert velocity between ft/s, m/s, mph, and km/h.
- View results in ft·lbf, joules, or kilojoules.
- Useful for shooters, hunters, engineers, and educators.
Table of Contents
How FPE Calculator Works?
The FPE calculator estimates a projectile's kinetic energy from its mass and velocity. Kinetic energy increases linearly with mass and with the square of velocity, so doubling the velocity produces four times as much energy when mass remains unchanged.
For the common combination of projectile mass in grains and velocity in feet per second, the foot-pounds of energy result is calculated as follows:
Here, E is the projectile energy in ft·lbf, m is projectile mass, and v is projectile velocity. The calculator accepts mass entered in gr, g, kg, oz, or lb and velocity entered in ft/s, m/s, mph, or km/h. The calculated result can be displayed in ft·lbf, J, or kJ. For example, a 124 gr projectile traveling at 1,100 ft/s produces approximately 333.2 ft·lbf of energy.
| Variable | Meaning | Supported entries |
|---|---|---|
| m | Projectile mass | gr, g, kg, oz, lb |
| v | Projectile velocity | ft/s, m/s, mph, km/h |
| E | Calculated energy | ft·lbf, J, kJ |
Practical Use Cases
Shooters can compare the energy of different ammunition loads by entering each projectile's mass and measured or published velocity, helping evaluate relative performance for a particular firearm and purpose.
Hunters can estimate the energy of a projectile at a stated velocity and compare loads when researching whether a cartridge may be suitable for a specific hunting application.
Engineers can use the calculator as a quick kinetic-energy estimate for projectile testing, impact studies, equipment design, and preliminary ballistic calculations.
Educators and students can demonstrate the relationship between mass, velocity, and kinetic energy by changing one input at a time and observing that velocity has a squared effect on the result.
Accuracy and Limitations
The calculator accurately evaluates the ideal kinetic-energy equation for the entered mass and velocity within the supported input ranges of 0.001 to 100,000 for mass and 0.001 to 5,000 for velocity, subject to the precision of the supplied measurements and displayed rounding. It calculates energy only at the specified velocity; it does not model air resistance, bullet shape, ballistic coefficient, gravity, barrel behavior, retained velocity, impact angle, deformation, or energy transfer to a target. Results should therefore be treated as theoretical projectile energy rather than a complete prediction of downrange or terminal performance.
Quick Examples
Example #1: Light airgun pellet
Estimate the energy of a lightweight pellet traveling at moderate velocity.
Example #2: Standard handgun projectile
Evaluate the energy of a medium-mass projectile using metric input units.
Example #3: Heavy rifle projectile
Estimate the energy of a heavier projectile at high velocity for ballistic comparison.
