Foot-Pounds Calculator (ft-lb)
Use this tool to calculate foot-pounds from force and distance, or convert ft-lb and N·m for quick torque and energy checks.
1) Calculate ft-lb from force and distance
2) Convert ft-lb to Joules, N·m, and in-lb
3) Convert N·m to ft-lb
What is a foot-pound?
A foot-pound (ft-lb) is a unit commonly used in the U.S. to describe work, energy, and torque. In basic terms, one foot-pound means applying one pound of force through a distance of one foot.
Formula:
Foot-pounds = Force (lb) × Distance (ft)
Quick examples
- If you apply 50 lb of force over 3 ft: 50 × 3 = 150 ft-lb
- If a wrench torque spec is 90 ft-lb, that means a turning force equivalent to 90 pounds applied at a 1-foot lever arm
- 300 ft-lb equals about 406.75 joules
Common conversions
ft-lb to joules
Use this conversion factor:
1 ft-lb = 1.355817948 joules
ft-lb to N·m
For torque values, the numeric conversion is the same:
1 ft-lb = 1.355817948 N·m
N·m to ft-lb
Reverse conversion:
1 N·m = 0.737562149 ft-lb
When people use an ft pounds calculator
- Automotive: Wheel lug nuts, spark plugs, and engine components often have torque specs in ft-lb or N·m.
- Mechanical projects: Bolts and fasteners need proper torque to avoid loosening or damage.
- Physics and engineering homework: Work and energy calculations are often presented in imperial units.
- Tool setup: Converting between inch-pounds and foot-pounds for torque wrenches.
Torque vs. energy: same numbers, different meaning
You may notice ft-lb and N·m show up for both energy and torque. The conversion numbers match, but the physical interpretation is different:
- Energy/work: force applied over linear distance.
- Torque: rotational force around a pivot.
In practical use, context tells you which one you’re dealing with. For example, a torque wrench spec is torque, not energy.
Tips for accurate results
- Use the correct unit type (lb-force, not lb-mass).
- Keep lever arm distance in feet for ft-lb calculations.
- Round only at the end to reduce cumulative error.
- For critical applications (engine internals, safety components), always follow manufacturer documentation.
Final thoughts
This ft pounds calculator is designed for quick, practical use: calculate foot-pounds, convert to joules and N·m, and reverse-convert N·m to ft-lb. Whether you’re working in a garage, workshop, classroom, or lab, clean unit conversion helps prevent costly mistakes and improves consistency.