Field Strength Converter
EMC and RF-exposure work quotes field strength in several units. This tool converts a far-field level between electric field (V/m and dBµV/m), magnetic field (A/m) and power density (W/m² and dBm/m²), all tied together by the free-space impedance of 377 Ω. You can also enter an EIRP and distance to get the field at that range.
Equations & Parameters ▸
\(E_{\text{dBµV/m}} = 20\log_{10}\dfrac{E}{1\,\text{µV/m}} \qquad S = \dfrac{E^2}{\eta_0},\quad H = \dfrac{E}{\eta_0}\)
far field: \(S = \dfrac{P_{\text{EIRP}}}{4\pi d^2},\qquad E = \sqrt{S\,\eta_0}\)
far field: \(S = \dfrac{P_{\text{EIRP}}}{4\pi d^2},\qquad E = \sqrt{S\,\eta_0}\)
| E | Electric field strength (V/m), or in dBµV/m (dB relative to 1 µV/m). |
| S | Power density (W/m²), or in dBm/m². |
| EIRP, d | Equivalent isotropic radiated power (dBm) and distance (m), for the far-field level. |
| η0 | Free-space impedance ≈ 376.73 Ω (used for all E↔H↔S conversions). |
References: H. Ott, Electromagnetic Compatibility Engineering, Wiley, 2009. · ICNIRP, Guidelines for Limiting Exposure to Electromagnetic Fields, 2020.
Inputs
Pick one
Field / power level
dBm
Far-field sourcem
RangeResults
Electric & magnetic
E-field—
E-field (dBµV/m)—
H-field—
Power density
S (W/m²)—
S (dBm/m²)—
S (mW/cm²)—
Diagram