E-field → Power Density & H-field
Convert electric field E (V/m) to power density (W/m², mW/cm²) and magnetic field H (A/m).
Worked example
Input: Electric field E 10 V/m
Result: Field strength 140 dBµV/m, Power density S 0.265442 W/m², Power density S 0.0265442 mW/cm², Magnetic field H 0.0265442 A/m
Result: Field strength 140 dBµV/m, Power density S 0.265442 W/m², Power density S 0.0265442 mW/cm², Magnetic field H 0.0265442 A/m
Formula
S = E² / η₀ (η₀ ≈ 376.73 Ω)
H = E / η₀
1 W/m² = 0.1 mW/cm²
How it works
For a plane wave (far field), power density S = E²/η₀ and H = E/η₀, with η₀ ≈ 376.73 Ω. Useful for exposure assessments, comparing test levels and estimating power at a test location.
Practical tipThis only holds in the far field. For near-field sources such as small loops the E/H ratio is not 376.73 Ω, so measure E and H separately.
Related calculators
Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10