Efficiency Calculator
This efficiency calculator finds the efficiency of a machine or process as a percentage from the useful output and the total input. Enter both and the efficiency calculator returns the efficiency and the loss. It applies the efficiency formula for energy, work, and power, so one tool covers physics, electrical, and machine problems.
Results
The Efficiency Calculator is part of our Machinery collection. Browse more machinery to size, convert, and check your work alongside this tool.
What the efficiency calculator shows
Efficiency is how much of what you put in comes out as useful work, written as a percentage. This efficiency calculator divides the useful output by the total input and multiplies by 100, then shows the loss. Whether you use it as an energy efficiency calculator, a work efficiency calculator, or a machine efficiency calculator, the ratio is the same.
Efficiency formula energy and work
The efficiency formula for energy divides the useful output by the total input:
Output and input use the same unit, so the result is a percentage from 0 to 100. No real machine reaches 100 percent, because some energy always leaves as heat, sound, or friction. This is the same efficiency formula calculator whether the quantity is energy, work, or power.
Efficiency calculator example
A motor that delivers 750 W of useful output from a 1000 W input. The efficiency calculator gives:
The loss is 250 W, turned into heat. Change either value and the efficiency calculator updates the percentage at once.
How to use the efficiency calculator
Enter the useful output and the total input in the same units, then the efficiency calculator returns the efficiency as a percentage and the amount lost. The output and input can be energy in joules, power in watts, or work in any consistent unit. Since both are in the same unit, the units cancel and the result is a clean percentage.
Reading the efficiency calculator result
The efficiency percentage tells you how much of the input does useful work; the rest is the loss. A higher percentage means less waste and a lower running cost. Efficiency can never exceed 100 percent, and a value above it means the output or input was entered wrongly. Use the loss figure to see how much energy is worth recovering, since cutting losses is often cheaper than adding input.
When to use the energy efficiency calculator
- Rating a motor or machine with the energy efficiency calculator
- Finding the loss in a power system with an electrical efficiency calculator
- Working a physics problem with the work efficiency formula
- Comparing two designs by their efficiency
Common efficiency calculator mistakes
- Different units. Output and input must share a unit, or the percentage is meaningless.
- Swapping output and input. Output goes on top; swapping them gives a value above 100 percent.
- Ignoring stages. Overall efficiency is the product of each stage, not the average.
Tips for efficiency
- Keep output and input in the same unit.
- Multiply stage efficiencies for the overall figure.
- Target the biggest loss first to improve a system.
The work efficiency formula
The work efficiency formula compares the useful work a machine does with the work put into it, and the formula for work efficiency is the same output over input ratio used everywhere else. A lever, pulley, or gear train can multiply force, but it never creates energy, so the work out is always a little less than the work in because of friction. That gap is the loss. A machine efficiency calculator turns this into a percentage so you can compare a rusty pulley with a well oiled one, or an old motor with a new one. The higher the number, the less work is wasted moving the machine itself rather than the load.
Electricity efficiency formula and machine efficiency
The electricity efficiency formula is the output over input ratio for electrical power, so an electrical efficiency calculator and a power efficiency calculator divide the watts delivered by the watts drawn. A power supply rated at 90 percent turns 90 of every 100 watts into useful output and loses 10 as heat, which is why efficient supplies run cooler. Energy conversion efficiency follows the same rule across every stage: a power plant, a transformer, and a motor each have their own efficiency, and the overall efficiency is the product of them. The lost energy becomes heat that has to be carried away, which is why efficient systems run cooler.
Efficiency formula calculator reference
Efficiency and loss for several output and input pairs, from the efficiency formula calculator:
| Output | Input | Efficiency | Loss |
|---|---|---|---|
| 750 | 1000 | 75% | 250 |
| 900 | 1000 | 90% | 100 |
| 400 | 500 | 80% | 100 |
| 950 | 1000 | 95% | 50 |
Efficiency Calculator FAQ
What is the efficiency formula?
The efficiency formula is efficiency = (output / input) times 100. The efficiency calculator applies it, with output and input in the same unit, to give a percentage.
Can efficiency be over 100 percent?
No. Some energy is always lost, so efficiency is below 100 percent. A value above it means the output or input was entered incorrectly.
What is the work efficiency formula?
The same ratio applied to work: useful work out divided by total work in, times 100. The work efficiency formula gives a percentage like any other efficiency.
Does it work for electrical efficiency?
Yes. As an electrical efficiency calculator, enter output and input power in watts. The electricity efficiency formula is the same output over input ratio.