Efficiency Calculator
Calculate mechanical, thermal, or electrical efficiency using η = (W_out / W_in) × 100%.
What Is Efficiency?
Calculate mechanical, thermal, or electrical efficiency using This calculator applies the formula in Efficiency contexts.
Understanding this relationship is fundamental to physics and engineering. The formula connects measurable quantities in a direct, predictable way.
Real-world applications span engineering design, scientific measurement, and everyday phenomena. The calculator handles unit conversions and shows alternates.
Common mistakes arise from unit errors and incorrect formula application. Always verify inputs are in SI units unless otherwise stated.
Formula Reference Table
| Solve For | Formula | Notes |
|---|---|---|
| Efficiency | η = (W_out / W_in) × 100% | Percentage |
| Output | W_out = η% × W_in / 100 | Same unit as input |
| Input | W_in = W_out / (η/100) | Same unit as output |
| Losses | W_loss = W_in − W_out | Wasted energy |
| Combined efficiency | η_total = η₁ × η₂ × η₃ (as decimals) | Cascade of devices |
| Carnot limit | η_max = 1 − T_c/T_h | For heat engines only |
3 Worked Examples
Motor: P_in=1000 W, P_out=850 W. Efficiency = 850/1000×100 = 85%.
- Losses = 150 W (heat in windings/bearings)
Coal plant: thermal input 1,000 MW, electrical output 380 MW. Efficiency?
- η = 380/1000 × 100 = 38%
- Losses: 620 MW as heat to cooling towers/stack
Battery→inverter(97%)→motor(93%)→gearbox(98%) = ηtotal.
- η_total = 0.97×0.93×0.98 = 88.4%
- Every 100 Wh from battery → 88.4 Wh to wheels
Real-World Applications
Common Mistakes to Avoid
Always convert to SI before calculating.
Check which version applies to your geometry.
Check positive/negative conventions.
Keep full precision until the final answer.
Many formulas involve v², f², or √(...) — double-check exponents.
Frequently Asked Questions
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Interpretation: This relationship connects motion, force, momentum, work or energy in a mechanical system. Assumption: Choose a consistent reference direction and unit system. The model may assume constant acceleration, rigid bodies, negligible losses or an isolated system.