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Conversion between linear and decibel units for electric/magnetic field strength, magnetic flux density and power density in free space. Default wave impedance ZW = √(µâ‚€/εâ‚€) ≈ 376.73 Ω (far-field plane wave, medium = air).
Relations (plane wave, medium = air): E / H = ZW, B = µâ‚€ · H, S = E · H = E² / ZW = H² · ZW

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Symbol

E

H

B

​

S

​​


Quantity

Electric field strength (RMS)

Magnetic field strength (RMS)

Magnetic flux density

​

Power density

​​


SI unit

V/m

A/m

T

​

W/m²

​

Wave impedance ZW

Ω

↺ Reset

E-FIELD

V/m

dBµV/m

H-FIELD

A/m

dBµA/m

B-FIELD

T

mT

pT

dBpT

Gs

POWER DENSITY S

W/m²

dBW/m²

dBm/m²

mW/cm²


Type in any field — all other fields update automatically. All values are RMS. The conversions assume a homogeneous medium and a plane wave (E ⊥ H, both ⊥ to direction of propagation).
Example: E = 10 V/m at ZW = 376.73Ω ≡ 140 dBµV/m ≡ H ≈ 26.55 mA/m ≡ S ≈ 0.265 W/m² ≡ −5.76 dBW/m²
 


References:
[1] J. L. Norman Violette, Donald R. J. White, Michael F. Violette, Electromagnetic Compatibility Handbook, Van Norstrand Reinhold Company, 1987, pp.26-29


 
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