Foot Pounds to Joules
Type a value in either box to convert between foot pounds and joules. The factor is 1.35582.
| Foot Pounds | Joules |
|---|---|
| 1 ft·lb | 1.355818 J |
| 2 ft·lb | 2.711636 J |
| 3 ft·lb | 4.067454 J |
| 5 ft·lb | 6.77909 J |
| 10 ft·lb | 13.558179 J |
| 25 ft·lb | 33.895449 J |
| 50 ft·lb | 67.790897 J |
| 100 ft·lb | 135.581795 J |
How to use
- Enter a value in the Foot Pounds field.
- The Joules figure appears immediately — no button to press.
- Typing in the Joules field converts back to Foot Pounds the same way.
- Use the reference table for the values that come up most often.
Foot Pounds to Joules formula
Converting foot pounds to joules is a single multiplication by 1.35581795.
J = ft·lb × 1.35581795
Why this factor: the foot-pound and the joule are both defined against the joule, so dividing one definition by the other gives 1.35581795 directly. Both definitions are set out in full below.
To go the other way, divide by 1.35581795 — or use the Joules to Foot Pounds converter, which is the same calculation reversed.
Worked example
Start with 2000 ft·lb. Multiply by 1.35581795 to get 2711.635897 J.
2000 ft·lb × 1.35581795 = 2711.635897 J
The converter above does this for any value you type, in either direction.
What is a foot-pound?
A foot-pound is the work done by one pound-force acting through one foot.
Definition: About 1.3558179 joules.
Where it is used: US mechanical work and torque figures, fastener specifications, and firearm muzzle energy.
Worth knowing: As a torque unit it is properly 'pound-foot' (lbf·ft); as an energy unit it is 'foot-pound'. The numbers coincide but the quantities differ.
What is a joule?
The joule is the SI unit of energy — the work done by one newton acting over one meter.
Definition: Defined as 1 N·m, equivalently one watt-second. Named after James Prescott Joule.
Where it is used: All scientific energy calculations, food energy on European labels, and mechanical work.
Foot Pounds vs Joules
The foot-pound is a US customary unit while the joule is an SI unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many joules are in a foot-pound?
One foot-pound equals 1.35581795 joules.
What is the formula to convert foot pounds to joules?
Multiply the number of foot pounds by 1.35581795. To reverse it, divide by 1.35581795 instead.
How do I convert joules back to foot pounds?
Divide by 1.35581795, which is the same as multiplying by 0.737562149.
How many joules are in 10 foot pounds?
10 ft·lb works out to 13.558179 J.
Is there anything to watch out for with foot pounds?
As a torque unit it is properly 'pound-foot' (lbf·ft); as an energy unit it is 'foot-pound'. The numbers coincide but the quantities differ.
How is the foot-pound defined?
About 1.3558179 joules.