FPE calculator — Foot-pounds of Energy

Q: How do I calculate foot-pounds of energy?

To calculate FPE: Note the weight of your projectile in grains. Square its velocity expressed in feet per second. Multiply the results of steps 1 and 2 together. Finally, divide the result obtained in step 4 by 450,240.

Q: What is the 45 ACP foot-pound of energy?

Around 369 ft-lb. Assuming you have a standard 45 ACP with a 230-grain bullet traveling at about 850 feet per second (ft/s), then you get the result with the following formula: FPE = (230 × 850²)/450,240 ≃ 369 ft-lbs

Q: Is 50 FPE lethal?

According to "Homicide Using an Air Weapon", the lethal force required for a projectile is 58 foot-pounds of energy (FPE) , but less powerful projectiles can still be fatal if they hit vital points.

Creators

Claudia Herambourg

Claudia Herambourg is an aspiring computational linguist with a passion for both words and numbers. She holds a Bachelor’s degree in English Literature and Mathematical Studies from University College Cork, Ireland. She is currently pursuing her Master’s degree in Linguistics at Sorbonne Nouvelle University in Paris, specializing in computational linguistics. In her spare time, you'll probably find her reading a book of Japanese literature that nobody has ever heard of, on a train going nowhere. See full profile

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Reviewers

Steven Wooding

Steven Wooding is a physicist by training with a degree from the University of Surrey specializing in nuclear physics. He loves data analysis and computer programming. He has worked on exciting projects such as environmentally aware radar, using genetic algorithms to tune radar, and building the UK vaccine queue calculator. Steve is now the Editorial Quality Assurance Coordinator here at Omni Calculator, making sure every calculator meets the standards our users expect. In his spare time, he enjoys cycling, photography, wildlife watching, and long walks. See full profile

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Whether you're passionate about ballistics, physics, engineering, or archery, this FPE calculator helps you instantly calculate the foot-pounds of energy and understand the kinetic energy behind bullets, pellets, arrows, or any other projectiles.
Keep reading and discover:

What is a foot-pound of energy?
How to calculate foot-pounds of energy (FPE)?
How to use our foot-pounds of energy calculator?
What is the 45 ACP foot-pound of energy?

Ready, aim, calculate!

What is a foot-pound of energy (FPE)?

FPE, short for foot-pound of energy (ft-lbs or ft-lbf), is a unit of work or energy used in the imperial and US customary systems. It is defined as the amount of energy required to exert a force of one pound over a distance of one foot. The corresponding SI unit is the joule, although in terms of energy, one joule is not equal to one foot-pound (1 foot-pound ≈ 1.3558 joules).

💡 Want to know more about energy conversion? Check out energy converter!

FPE calculation formula: How to calculate FPE (foot-pounds of energy)?

You can easily calculate foot-pounds of energy using this kinetic energy formula:

\text{FPE} = \frac{w \times v^2}{450,\!240}

where:

$\text{FPE}$ — Foot-pounds of energy (ft-lbs);
$w$ — Weight of the projectile in grains (gr); and
$v$ — Velocity of the projectile in feet per second (ft/s or fps).

Example

Suppose you want to know the FPE of a bullet weighing 150 grains travelling at 2,800 ft/s. Input these numbers into the FPE calculation formula:

\text{FPE} = \frac{150 \times 2,\!800^2}{450,\!240} \approx \text{2,612 ft-lbs}

You get 2,612 ft-lbs.

If you want to skip the math and plug in your numbers directly, try our bullet energy calculator!

How to use the FPE calculator

Using our foot-pounds of energy calculator is quick and straightforward:

Enter the projectile's weight (in grains).
Input the projectile's velocity (in feet per second).
That's it! The result in foot-pounds of energy appears automatically in the third field, FPE.

But the calculator can do more than calculate FPE! If you already know a projectile's energy and weight (or speed), you can reverse the formula to find its speed (or weight). For example, if you know the energy of an arrow and its weight, this tool will calculate its velocity.

Want to learn more about archery? Check out our dedicated arrow speed calculator.

Why use a foot-pounds of energy calculator?

People often ask, "How to calculate foot-pounds of energy?" and while an FPE calculator provides a quick answer, what's important is what the calculation teaches you. Well, it basically gives a straightforward understanding of a projectile's power and energy transfer. Here are some examples of important uses you may encounter one day:

Ballistics: Hunters and shooters can compare bullets' stopping power. A conventional 9mm bullet has approximately 350 to 400 foot-pounds of energy.
Archery and air guns: Bow hunters and air gun users rely on the accuracy of arrows or pellets' FPE to hunt.
Physics and engineering: An FPE calculator can help measure energy transfer in machines or classroom experiments.
Accuracy and speed: It can prevent mathematical errors and provide instant, reliable results.

FAQs

How do I calculate foot-pounds of energy?

To calculate FPE:

Note the weight of your projectile in grains.
Square its velocity expressed in feet per second.
Multiply the results of steps 1 and 2 together.
Finally, divide the result obtained in step 4 by 450,240.

What is the 45 ACP foot-pound of energy?

Around 369 ft-lb. Assuming you have a standard 45 ACP with a 230-grain bullet traveling at about 850 feet per second (ft/s), then you get the result with the following formula:

FPE = (230 × 850²)/450,240 ≃ 369 ft-lbs

What is FPE for air gun?

When it comes to air guns, we like to talk about "muzzle energy", which is the kinetic energy of a projectile when it is expelled from the muzzle of an air gun. This type of energy, measured in foot-pounds of energy or FPE, accurately represents the power of an air gun.

Is 50 FPE lethal?

According to "Homicide Using an Air Weapon", the lethal force required for a projectile is 58 foot-pounds of energy (FPE), but less powerful projectiles can still be fatal if they hit vital points.