🎯 FPE Calculator
Calculate Foot-Pounds of Energy
How to Use This Calculator
Enter Bullet Mass
Input the bullet mass in grains. One grain equals 0.0000648 kg. Common bullet weights range from 55-300 grains for most ammunition. You can find this value on ammunition boxes or specifications.
Enter Bullet Velocity
Enter the bullet velocity in feet per second (fps). Typical handgun velocities range from 800-1400 fps, while rifle bullets can exceed 3000 fps. This is often listed on ammunition boxes or can be measured with a chronograph.
Calculate FPE
Click the "Calculate" button to compute the foot-pounds of energy. The calculator converts grains and fps to metric units, calculates kinetic energy, and converts the result to foot-pounds.
Review Results
Review the calculated FPE in foot-pounds and the equivalent energy in Joules. FPE is commonly used in ballistics to compare ammunition performance and determine appropriate loads for different applications.
About FPE Calculator
The FPE (Foot-Pounds of Energy) Calculator computes the kinetic energy of projectiles in foot-pounds, a unit commonly used in ballistics and hunting. FPE is derived from the kinetic energy formula and provides a standardized way to compare ammunition performance across different calibers and loads.
When to Use This Calculator
- Hunting Applications: Determine appropriate FPE for different game sizes and hunting regulations
- Ammunition Comparison: Compare energy output across different bullet weights and velocities
- Ballistics Analysis: Calculate stopping power and terminal ballistics
- Reloading: Verify energy calculations for custom loads
- Safety Planning: Understand bullet energy for range safety and barrier design
Why Use Our Calculator?
- ✅ US Units: Uses grains and fps, common in American ballistics
- ✅ Dual Output: Provides results in both foot-pounds and Joules
- ✅ Accurate Conversion: Properly converts between units
- ✅ Instant Results: Get answers immediately
- ✅ Free to Use: No registration or payment required
Understanding FPE
Foot-pounds of energy (FPE) is the kinetic energy of a projectile expressed in foot-pounds. It's calculated from mass and velocity using the kinetic energy formula, then converted to foot-pounds. FPE values vary widely: rimfire rounds typically produce 50-200 FPE, handgun rounds 300-800 FPE, and rifle rounds can exceed 4000 FPE. Higher FPE generally means more stopping power, but bullet design and shot placement are equally important.
Formula
KE = ½mv²
FPE = KE × 0.737562 (Joules to foot-pounds)
FPE = (mass × velocity²) / 450240 (direct from grains and fps)
Where:
- FPE = Foot-Pounds of Energy
- KE = Kinetic Energy (Joules)
- m = Mass (grains or kg)
- v = Velocity (fps or m/s)
Example Calculation:
For a bullet with mass = 150 grains and velocity = 1000 fps:
First, convert to metric: m = 150 × 0.0000648 = 0.00972 kg
v = 1000 × 0.3048 = 304.8 m/s
KE = ½ × 0.00972 × (304.8)² = 451.5 J
FPE = 451.5 × 0.737562 = 333 ft·lb
Frequently Asked Questions
What is FPE and why is it important?
FPE (Foot-Pounds of Energy) measures a bullet's kinetic energy in foot-pounds. It's important because it indicates stopping power and potential damage. Higher FPE means more energy transferred to the target, which is crucial for hunting effectiveness and safety considerations. However, bullet design, shot placement, and penetration characteristics also matter.
How do I convert grains to grams or kilograms?
1 grain = 0.0648 grams = 0.0000648 kg. To convert grains to grams, multiply by 0.0648. For example, 150 grains = 9.72 grams. To convert grains to kg, multiply by 0.0000648.
How do I convert fps to m/s?
To convert feet per second (fps) to meters per second (m/s), multiply by 0.3048. For example, 1000 fps = 304.8 m/s. To convert m/s to fps, multiply by 3.28084.
What is a typical FPE for different calibers?
Typical FPE values: .22 LR (rimfire) 100-150 FPE, 9mm handgun 300-400 FPE, .45 ACP 350-450 FPE, .223 Remington (rifle) 1200-1300 FPE, .308 Winchester 2500-2800 FPE, and large calibers like .50 BMG can exceed 12,000 FPE. These values vary with bullet weight and velocity.
How much FPE do I need for hunting?
Recommended minimum FPE varies by game: small game (squirrels, rabbits) 100-200 FPE, medium game (deer) 1000-1500 FPE, large game (elk, moose) 2000+ FPE. However, these are general guidelines—shot placement, bullet design, and local regulations are also important factors. Always check local hunting regulations for specific requirements.