Battery efficiency calculator

Round-trip or energy efficiency η = 100 × (useful out / energy in) with consistent units.

Calculator

Model / formula

η = 100 × (useful energy out / energy in) — use consistent units (J, Wh, …)

Useful energy delivered (e.g. Wh)

Energy stored / charged in (same unit)

$$\eta = 100 \times \frac{E_{\text{out}}}{E_{\text{in}}}$$

When to use

Comparing real batteries or teaching definitions of Coulombic vs energy efficiency (this tool is generic energy ratio).

Educational use only. Double-check values for labs, homework, and exams.