Work out dipole antenna length instantly with clear inputs, formula shown and shareable results.
A half-wave dipole is about 0.95 x lambda/2 long in practice, split into two equal legs. Its feed impedance is 73 ohms in free space but varies strongly with height above ground, dropping toward 40 ohms below a quarter wavelength and peaking above it — which is why SWR changes when a dipole is raised.
Dipole length
total = 0.5 x lambda x 0.95; each leg is half of that; 143 / f(MHz) metres is the handy shortcut
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
Total length in metres is about 143 divided by frequency in MHz, or 468 divided by frequency in MHz for feet.
Ground reflection couples back into the antenna, adding or subtracting from the radiation resistance depending on the phase, which depends on height in wavelengths.