E-Field to H-Field Converter

Convert between electric field (E) and magnetic field (H) strength under plane-wave far-field conditions.

Use this when: You are working with antenna equations, shielding calculations, or correlating E-field and H-field probe readings.

Reference only. Verify against your calibrated setup, antenna calibration data, and the applicable standard before making compliance decisions.

Key formula

H (A/m) = E (V/m) / 377 · dBµA/m = dBµV/m − 51.5

Example: Enter 377 V/m → 1 A/m (or 120 dBµV/m → 68.5 dBµA/m)

Valid for far field / plane wave conditions only. η = 377 Ω is the wave impedance of free space.

Electric field

V/m

Magnetic field

A/m

E-field (log)

dBµV/m

H-field (log)

dBµA/m

E-field to H-field in the far field

In a plane-wave far field, the magnitude of E and H are linked by the impedance of free space: E/H ≈ 377 Ω. This converter applies that relationship so you can move between V/m and A/m (or their dB forms) when the wave is actually a plane wave.

It is the wrong tool in the near field of a loop or a small clock, where E and H are not locked together. Use it for antenna equations, shielding estimates, and correlating E- and H-field probe readings only after you have checked the distance versus wavelength.

Frequently asked questions

Quick answers about using this calculator

What impedance does E/H use?

Free-space intrinsic impedance, about 377 Ω, under plane-wave far-field conditions.

Can I use this next to a switching PSU?

Usually not. That is a near-field problem. Measure E and H separately or use the probe the standard names.

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