Free Foot-Pounds of Energy Calculator
Calculate energy in foot-pounds (ft-lbf) for moving objects or lifted objects. You can also see the equivalent in joules.
What is a foot-pound of energy?
A foot-pound of energy (ft-lbf) is a unit of work or energy in the imperial system. One foot-pound means enough energy to move a one-pound force through a distance of one foot. It is widely used in ballistics, engineering, mechanics, and equipment ratings.
People often use foot-pounds to compare the impact energy of ammunition, tools, bows, air rifles, and moving machinery. If you work internationally, you may also need joules. This calculator gives both.
Formulas used in this calculator
1) Kinetic Energy (moving object)
The underlying physics formula is:
In this equation, m is mass (in slugs for imperial consistency) and v is velocity in ft/s. For bullet and projectile work, you will often see the shortcut:
2) Potential Energy (lifted object)
If you lift a weight, the energy stored is:
How to use the foot pounds of energy calculator
- Choose Kinetic Energy for projectiles, vehicles, moving parts, or any object with speed.
- Choose Potential Energy for lifting, hoisting, climbing, or stored gravitational energy.
- Enter positive values only (no negatives).
- Click Calculate Energy to get ft-lbf and joules.
Example calculations
Ballistics example
A 150-grain projectile traveling at 2,800 fps has approximately: 2,611 ft-lbf of kinetic energy (about 3,540 joules).
Mechanical lifting example
Raising a 200 lbf load by 3 feet stores: 600 ft-lbf (about 813.5 joules) of potential energy.
Why foot-pounds matter
- Ballistics: Compare cartridges, arrows, and airgun performance.
- Fitness & work: Estimate work done in lifting and repetitive movement.
- Mechanical systems: Evaluate springs, impacts, and motion energy.
- Safety: Understand hazard levels around moving equipment.
Foot-pounds and joules conversion
Use this quick relationship:
- 50 ft-lbf ≈ 67.79 J
- 100 ft-lbf ≈ 135.58 J
- 500 ft-lbf ≈ 677.91 J
- 1000 ft-lbf ≈ 1355.82 J
FAQ
Is foot-pound of energy the same as foot-pound of torque?
They use similar-looking units but represent different physical quantities. Torque is rotational force; energy is the capacity to do work.
Is kinetic energy enough to judge real-world performance?
Not always. In ballistics, factors like bullet construction, penetration, shot placement, and velocity at target also matter. Energy is important, but it is only one piece of the puzzle.
Can I enter velocity in miles per hour?
This calculator expects feet per second for kinetic mode. Convert mph to fps first: fps = mph × 1.46667.