nmtoftlbs.org › ft·lb to J

Foot-Pounds of Energy to Joules Converter

Convert foot-pounds of energy to joules (J) and back. This is the foot-pound used for work and energy, such as muzzle energy, not the foot-pound used for torque, even though they are written the same way.

Foot-Pounds (energy) ⇄ Joules
ft·lb
=
J
Result100 ft·lb = 135.58 J
Quick answer
One foot-pound of energy is 1.35582 joules, so multiply foot-pounds by 1.35582 to get joules. A 100 ft·lb figure is about 135.6 J. This is the energy foot-pound, force carried through a distance, the way muzzle energy is quoted. It is not the torque foot-pound (a twist), even though the words and the factor look identical. To reverse, multiply joules by 0.73756.

Conversion table

Foot-pounds (ft·lb)Joules (J)
1 ft·lb1.36
10 ft·lb13.56
25 ft·lb33.9
50 ft·lb67.79
100 ft·lb135.58
250 ft·lb338.95
500 ft·lb677.91
1000 ft·lb1355.82

How to convert ft·lb to J

J = ft·lb × 1.35582reverse: ft·lb = J × 0.73756
ft·lb
foot-pounds of energy you enter
J
the result in joules
1.35582
joules in one foot-pound of energy

The energy foot-pound and the torque foot-pound share a name and the same numerical factor to the metric side, but they are different quantities. Energy is force along a line, torque is force on a lever arm. Ballistics and physics use the energy one; wrenches use the torque one.

If your value is a torque spec, use newton-metres to foot-pounds instead, which converts twist. This page converts energy.

Frequently asked questions

How many joules is 100 ft-lb of energy?

100 foot-pounds of energy is about 135.6 joules.

How many foot-pounds is 200 J?

200 joules is about 147.5 foot-pounds of energy.

Is this the same as the torque foot-pound?

No. The factor to metric is the same number, but energy and torque are different quantities, so keep them apart.

Why is muzzle energy in foot-pounds?

It is customary in the shooting world; the figure is the kinetic energy of the projectile, which converts straight to joules here.

What is 1 joule in foot-pounds of energy?

One joule is about 0.7376 foot-pounds of energy.

Quick facts
1 foot-pound (energy)
1.35582 J
1 joule
0.7376 ft·lb
Quantity
Energy
Not
torque