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FPE Calculator

Enter the velocity and the weight of the grain in the calculator, and the tool will calculate the FPE.

Related

An FPE calculator helps users determine the kinetic energy of a pellet or BB as it exits the barrel of a handgun or rifle. This value represents the actual power of the airgun, helping you choose the right firearm based on performance requirements.

What is FPE (Foot-Pounds of Energy)?

A foot-pound (ft·lb) is a unit used to measure muzzle energy. It represents the amount of kinetic energy a projectile possesses at the moment it leaves the barrel of a gun.

One foot-pound is defined as the energy required to move a one-pound object through a distance of one foot using a force of one pound.

FPE Calculation Formula:

The formula used to calculate Foot-Pounds of Energy (FPE) is:

FPE = (V)² × (W / 450240)

V = velocity of the projectile (feet per second, ft/s)
W = projectile weight (grains)

Instead of performing manual calculations, you can use an online FPE calculator. Simply enter velocity and projectile weight, and the tool will instantly compute the muzzle energy.

How to Manually Calculate FPE?

Follow these steps:

Determine the projectile weight in grains.
Measure or obtain the projectile velocity in ft/s.
Square the velocity value.
Multiply the squared velocity by the projectile weight.
Divide the result by 450240.

The final result will be expressed in Foot-Pounds of Energy (ft·lb).

Example:

Suppose the projectile weight is 12.5 grains and the velocity is 800 ft/s. Calculate the FPE.

Solution:

Given:

Weight (W) = 12.5 grains

Velocity (V) = 800 ft/s

Step 1: Square the velocity

800² = 640,000

Step 2: Multiply by weight

640,000 × 12.5 = 8,000,000

Step 3: Divide by 450240

FPE = 8,000,000 / 450240 ≈ 17.77 ft·lb

Working of Online FPE Calculator:

Inputs:

Enter projectile velocity (ft/s).
Enter projectile weight (grains).
Click Calculate.

Output:

Foot-Pounds of Energy (FPE)
Step-by-step calculation details

FAQs:

How Many Ft·Lbs is 800 FPS?

If an 8-grain projectile travels at 800 ft/s:

FPE = (800² × 8) / 450240

FPE = (640,000 × 8) / 450240

FPE = 5,120,000 / 450240 ≈ 11.37 ft·lb

What is Ft·Lbs of Muzzle Energy?

Muzzle energy is the kinetic energy a projectile carries as it exits the barrel of a firearm. It indicates the potential impact power of the pellet or bullet and is measured in Foot-Pounds of Energy (ft·lb).