Antenna Length Calculator

Calculate physical antenna lengths for common antenna types at any frequency.

What is antenna length?

An antenna's length is tuned like a guitar string — the right length resonates at the right frequency. Cut it too short or too long and it won't radiate efficiently, wasting power as heat instead of sending a signal.

Why does this matter?

FM radio antennas are about 75 cm long because that's the right length for 100 MHz. WiFi antennas are tiny — just a few centimeters — because they operate at 2.4 GHz. Each antenna is precisely matched to its frequency.

Parameters
Set the operating frequency and conductor velocity factor.

The frequency your antenna needs to transmit or receive. For example, 144 MHz is the 2-meter amateur radio band, 2400 MHz is WiFi.

How fast the signal travels through your wire compared to the speed of light. Bare wire is nearly 1.0; coaxial cable is closer to 0.66. Use 0.95 for most wire antennas.

Antenna Type

Half-wave Dipole

The fundamental resonant antenna. Total length is half the wavelength.

Feed: ≈ 73 Ω× 0.5 λ

Each arm is λ/4. Common in HF/VHF applications.

Physical Length
Half-wave Dipole at 144 MHz
Length (meters)0.9896 m
Length (centimeters)98.96 cm
Length (feet)3.2467 ft
Length (inches)38.960 in

These are theoretical resonant lengths. Actual antenna length may require trimming due to end effects, nearby conductors, and mounting geometry. Always measure and tune with an antenna analyzer.