Question 1

What is FPE (Foot-Pound Energy)?

Accepted Answer

FPE (Foot-Pound Energy) is a unit of measurement for kinetic energy used primarily in ballistics and hunting. It represents the energy of a moving projectile (bullet, arrow, pellet) and is expressed in foot-pounds (ft-lbs). One foot-pound is the energy required to raise one pound one foot against gravity. FPE is calculated using projectile weight and velocity to determine striking power.

Question 2

How do you calculate foot-pound energy?

Accepted Answer

FPE is calculated using the formula: FPE = (Weight × Velocity²) ÷ 450,240. Where weight is measured in grains, velocity in feet per second (fps), and the result is in foot-pounds. For example, a 150-grain bullet traveling at 2,800 fps produces: (150 × 2,800²) ÷ 450,240 = 2,611 ft-lbs. The constant 450,240 converts the units to foot-pounds.

Question 3

What is the minimum FPE for deer hunting?

Accepted Answer

Most states and hunting experts recommend a minimum of 1,000 ft-lbs of energy for ethical deer hunting. However, many experienced hunters prefer 1,200-1,500 ft-lbs for reliable performance at typical hunting ranges. For larger deer or longer shots, 1,500+ ft-lbs is recommended. These guidelines ensure adequate penetration and energy transfer for quick, humane kills.

Question 4

How much kinetic energy does an arrow need?

Accepted Answer

For bowhunting deer-sized game, arrows should have at least 40 ft-lbs of kinetic energy, with 50-65 ft-lbs being ideal. For elk and larger game, 65-75+ ft-lbs is recommended. Unlike bullets that rely on expansion and shock, arrows kill through cutting, so momentum and penetration are equally important. Heavy arrows with moderate speed often penetrate better than light, fast arrows.

Question 5

What's the difference between FPE and momentum?

Accepted Answer

FPE (kinetic energy) measures the work capacity of a projectile, calculated as ½mv². Momentum measures the force required to stop the projectile, calculated as mass × velocity. For hunting: energy is important for tissue damage and expansion, while momentum is crucial for penetration. Heavy, slow projectiles have high momentum but lower energy; light, fast projectiles have high energy but lower momentum.

Question 6

How does FPE affect bullet performance?

Accepted Answer

Higher FPE generally means more energy transferred to the target, causing greater tissue damage and hydrostatic shock. However, FPE alone doesn't determine effectiveness—bullet construction, shot placement, and energy retention at range matter equally. A bullet with 2,000 ft-lbs at the muzzle might only have 1,200 ft-lbs at 300 yards. Match cartridge energy to game size and hunting range.

Question 7

What is a good FPE for self-defense?

Accepted Answer

For handgun self-defense, 300-400 ft-lbs is generally considered adequate with proper ammunition. Popular defensive calibers: 9mm (~350 ft-lbs), .40 S&W (~450 ft-lbs), .45 ACP (~400 ft-lbs). However, shot placement, bullet expansion, and penetration depth (12-18 inches) are more important than raw energy. FBI standards emphasize penetration over energy for defensive ammunition.

Question 8

How do you convert joules to foot-pounds?

Accepted Answer

To convert joules to foot-pounds: FPE = Joules × 0.737562. For example, 1,000 joules = 737.56 ft-lbs. To convert foot-pounds to joules: Joules = FPE × 1.35582. This conversion is useful when comparing American ballistics data (ft-lbs) with international specifications (joules). Many European ammunition is rated in joules rather than foot-pounds.

Question 9

What FPE do you need for big game hunting?

Accepted Answer

Big game energy requirements: Elk: 1,500-2,000 ft-lbs minimum, 2,000+ recommended. Moose: 2,000-2,500 ft-lbs. Bear: 1,500-2,000 ft-lbs (depending on species). African plains game: 2,000-3,000 ft-lbs. Dangerous game (elephant, buffalo): 4,000-6,000+ ft-lbs. These are guidelines—proper bullet construction and shot placement remain most critical for ethical, effective harvests.

Question 10

How is power factor different from FPE?

Accepted Answer

Power Factor (PF) is used in competitive shooting and equals bullet weight (in pounds) × velocity (fps) × 1,000. Unlike FPE which measures energy, PF is a linear scoring metric for competition divisions: Minor PF = 125-165, Major PF = 165+. PF doesn't account for the velocity squared effect on energy. A higher PF doesn't necessarily mean more stopping power—it's primarily for competition classification.

FPE Calculator - Foot Pound Energy Calculator & Ballistics Energy Calculator

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The FPE Formula

Understanding Kinetic Energy in Ballistics

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