How to Use Thermal Efficiency Calculator
The Thermal Efficiency Calculator quantifies how much of the heat supplied to a cycle is converted into useful work. Pick the formulation that matches your data and the Thermal Efficiency Calculator instantly returns η as a fraction and as a percent.
- Choose mode — Work-based (η = W/Qin) or heat-rejection-based (η = 1 − Qout/Qin).
- Enter energies — All values share units (kJ, MJ, or BTU); the Thermal Efficiency Calculator only needs consistency.
- Read η — Output is shown as 0–1 and 0–100 %.
Formula & Theory — Thermal Efficiency Calculator
η = W / Qin (work-based)
η = 1 − Qout / Qin (heat-rejection-based)| Symbol | Meaning |
|---|---|
| η | Thermal efficiency (dimensionless) |
| W | Net work output |
| Qin | Heat supplied to the cycle |
| Qout | Heat rejected by the cycle |
By the first law, W = Qin − Qout for a cyclic device. The Thermal Efficiency Calculator simply rearranges this energy balance.
Assumptions and Limits
The Thermal Efficiency Calculator assumes steady, cyclic operation. For real engines, friction, leakage, and incomplete combustion can change η over time. Compare your result to the Carnot limit 1 − Tcold/Thot to see how close the cycle gets to the theoretical maximum.
Use Cases for Thermal Efficiency Calculator
- Power plants — Compare Rankine and Brayton cycle efficiencies.
- Automotive — Benchmark internal-combustion or hybrid powertrains.
- HVAC and refrigeration — Convert COP/EER into equivalent η values.
- Education — Connect first-law accounting to real-world performance.
The Thermal Efficiency Calculator delivers a single number that captures how good a thermodynamic cycle is at turning heat into work.