Work and Power Calculator
Mechanical work in joules plus power in watts from force and time.
What it does
Mechanical work multiplies force by distance moved along the push. Lifting, dragging, and pressing all convert effort into energy this way, measured in joules or foot pounds.
The tool above takes force, distance, and seconds in metric or imperial. It returns work with average power beside it, plus the cross system equivalent.
The default of 50 N over 10 m in 4 s does 500 J (369 ft-lb) at 125 W. The imperial mirror of 100 lbf over 5 ft in 2 s does 500 ft-lb (678 J) at 250 ft-lb/s.
Definitions follow NASA work references with the same force times distance treatment in Khan Academy physics units. Both assume steady force along the motion; angled pushes need the cosine component.
How to use
- Pick metric or imperial for force and distance.
- Enter the steady force in N or lbf.
- Enter the distance moved along the push.
- Enter the seconds the push took.
- Read work first, then power for the rate.
Formula
- force
- Steady push along the motion.
- distance
- Meters or feet moved with the push.
- time
- Seconds dividing work into power.
Imperial converts first (1 lbf = 4.44822 N, 1 ft = 0.3048 m), then runs metric physics, so systems agree. Holding still burns effort but does zero mechanical work.
Worked example
Example: 50 N over 10 m in 4 s
Metric defaults: 50 N, 10 m, 4 s.
- Work: 50 x 10 = 500 J.
- Foot pounds: 500 x 0.7375621493 = 369 ft-lb.
- Power: 500 / 4 = 125 W.
- Check: 125 W for 4 s rebuilds 500 J.
- Tool shows 500 J, 125 W, 369 ft-lb.
Reference table
| Task | Work | Power |
|---|---|---|
| Lift 10 kg 1 m in 2 s | 98 J | 49 W |
| Example here | 500 J | 125 W |
| Climb stairs fast | 1500 J | 500 W |
| 1 hp for 1 s | 746 J | 746 W |
Limits
- Steady force assumed; varying pushes need integrals.
- Along motion only; sideways force does no work.
- Friction and drag excluded.
- Human efficiency (~25%) sits outside: bodies burn more.
Common mistakes
- Counting holding force as work done.
- Mixing lbf with meters without converting.
- Reading watts as total energy instead of rate.
- Ignoring the angle of angled pushes.
- Forgetting efficiency losses in real lifts.
Try it yourself
Quick checks. Answers sit tucked under each question.
100 lbf over 5 ft in 2 s?
500 ft-lb (678 J) at 250 ft-lb/s.
200 N over 3 m?
600 J regardless of time; power needs seconds.
Power holding 500 N still?
Zero work, zero power: no distance moved.
Questions
What is a joule?
One newton over one meter. 50 N over 10 m is 500 J.
Work vs power?
Work totals energy; power divides by time. Same lift faster means more watts.
How many watts is 1 hp?
746 W. Human bursts top near 1000 W briefly.
Does holding count?
No mechanical work without distance, though muscles still burn fuel.
Angled pushes?
Multiply by cosine of the angle; only the along part works.
Why add time?
Time turns total work into power, the rate engines and bodies sustain.