Dipole Antenna Calculator
A thin half-wave dipole is the fundamental antenna reference. At resonance it has ≈73 Ω feed impedance and 2.15 dBi gain. Practical dipoles are slightly shorter than λ/2 (shortening factor k ≈ 0.95–0.98) to account for end effects.
Equations & Parameters ▸
\(\ell_{arm} = \dfrac{k\lambda}{4} = \dfrac{kc}{4f}\)
| f | Resonant frequency. Sets λ and therefore physical length. |
| k | Shortening factor (0–1). Accounts for finite wire diameter; typically 0.95–0.98. |
| Arm | One arm of the dipole (total length = 2 × arm). |
| λ/2 | Free-space half-wavelength. |
| Monopole | Quarter-wave monopole over ground = half-arm length. |
Physical constants used
| c | Speed of light = 2.998×10⁸ m/s |
| µ₀ | Permeability of free space = 4π×10⁻⁷ H/m ≈ 1.2566×10⁻⁶ H/m |
| ε₀ | Permittivity of free space = 8.854×10⁻¹² F/m |
Inputs
0.95–0.98 for thin wire dipole
Results
Dimensions
Arm length—
Total dipole (λ/2)—
Monopole length (λ/4)—
Reference
Free-space wavelength, λ—
Diagram