The separation distance from an antenna can be divided into several regions. The transition between these regions is not distinct and the changes in antenna performance will be gradual. The regions depend on the maximum linear dimension of the antenna and the wavelength. This tool that will calculate the near-field and far-field distances based on the antenna dimension and wavelength.

For electrically small antennas (where D < λ / 2) there are only two regions; near-field and far-field. For electrically large antennas there are three regions; reactive near-field, radiating near-field and the far-field distance.

Calculation:

Formulas:

D Largest antenna dimension
λ represents wavelength in meters
C is the velocity factor 299,792,458 meters per second
Freq is the Frequency in cycles per second