Antenna Near-Field / Far-Field Boundary Calculator
Work out where an antenna's reactive near field, Fresnel (radiating near) region and far field begin — and check which region a measurement distance falls in.
Far-field distance at common frequencies
| Frequency | Wavelength | Fraunhofer distance |
|---|
The far-field (Fraunhofer) boundary is r = 2D²/λ and the outer edge of the radiating near field is r = 0.62·√(D³/λ), where D is the largest antenna dimension and λ = c/f. Closer than 0.62·√(D³/λ) the field is the reactive near field, where energy stores and returns to the antenna rather than radiating away. Both expressions assume D is much larger than λ, a single isolated antenna, and free space; a ground plane, a radome, nearby metal or a large array changes the practical boundary. Pattern and gain measurements usually need a little more than the 2D²/λ distance, and near-field measurement systems intentionally work inside it. Everything runs locally in your browser.