Efficiency of a Machine Calculator
Find a machine’s efficiency from its useful output and energy input, and see how much is wasted.
How it works
efficiency % = (useful output ÷ energy input) × 100 · energy wasted = input − output
Efficiency is the fraction of the energy you put in that comes out as useful work or power, expressed as a percentage. The rest is not destroyed — energy is conserved — but is lost to friction, heat, sound and other unwanted forms, which is why real machines never reach 100%. The same ratio works whether you compare energies (joules) or powers (watts), as long as input and output share the same units.
Worked example
A motor draws 1000 J and delivers 750 J of useful work: efficiency = (750 ÷ 1000) × 100 = 75%. The remaining 250 J — 25% — is wasted, mostly as heat in the windings and friction in the bearings.
Sources: Mechanical efficiency — Wikipedia
Frequently asked questions
Can a machine be more than 100% efficient?
No. That would mean it produces more useful energy than it consumes, violating conservation of energy. If a calculation gives over 100%, either the output was overstated or a hidden energy input was missed.
Where does the wasted energy go?
Mostly into heat from friction and electrical resistance, plus some sound and vibration. It is not destroyed — energy is always conserved — but it leaves in forms you cannot use for the intended task.
Does efficiency use energy or power?
Either, as long as both figures use the same measure and units. Output ÷ input gives the same percentage whether you compare energy in joules or power in watts, because time cancels.
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This calculator is for educational purposes. Double-check important results before acting on them.