Get "10 RF Design Principles Every Engineer Should Know" Free
Learn practical principles for better RF circuits, PCB layouts, simulations, measurements, and troubleshooting.
Calculators / Antenna Length
Antenna Length
Calculator
The essential general-purpose antenna length calculator. Calculate the physical length for a dipole, quarter-wave, half-wave, or full-wave antenna at any frequency β with velocity factor and conductor diameter corrections. The pillar calculator for any RF project.
Dipole / Quarter-wave
Half-wave
Full-wave
β Antenna Length Engine
Dipole
L = Ξ»/2
Quarter-Wave
L = Ξ»/4
Half-Wave
L = Ξ»/2
Full-Wave
L = Ξ»
Free-space Ξ» = β m
Bare metal β 0.95β0.98. Insulated wire β 0.66β0.85
Affects length via thick-element correction
Material affects effective velocity factor
Advanced Parameters
End capacitance shortening (0.95β0.98). Dipoles only.
m
Affects feedpoint impedance via image theory
For quarter-wave monopole on ground plane
L = Ξ»/n. 2=half-wave, 4=quarter-wave, 1=full-wave
All Antenna Types β This Frequency
| Type | Fraction | Length | Half-Length | Zin (approx) | Gain |
|---|---|---|---|---|---|
| Enter values above | |||||
Calculated Results
Dipole Length (L)
βm
Half-Length (L/2)β
Free-space Ξ»β
Ξ» in conductorβ
Length / Ξ»β
Feedpoint Impedanceβ
Gain (dBi)β
Bandwidth (approx)β
Thick-element correctionβ
Length in inchesβ
Length in feetβ
Select antenna type and enter frequency to calculate.
π Antenna Length Theory
All resonant antenna lengths are simple fractions of the operating wavelength Ξ». The wavelength in free space is Ξ» = c/f, but the physical antenna is always slightly shorter due to the velocity factor and end effects.
General Formula
L = (k Γ c) / (n Γ f)
k = velocity factor, c = 3Γ10βΈ m/s, n = divisor (1, 2, 4β¦), f = frequency in Hz
Practical Shorthand
Dipole: L(m) = 143/f(MHz)
Quarter-wave: L(m) = 71.5/f(MHz)
Full-wave: L(m) = 286/f(MHz)
These classic shortcuts include VF β 0.95 and end-effect β 0.97.
The velocity factor k accounts for the fact that electromagnetic waves travel slightly slower in real conductors than in free space. For bare copper or aluminium tubes, k β 0.95β0.98.
The end-effect further shortens the dipole by β3% due to capacitance at the wire tips. This is automatically included in the standard 143/f formula.
π‘ Antenna Shape & Pattern Viewer
Live Preview
|
β Shape & radiation pattern scale with type
View Mode
Frequency
144 MHz
1 MHz1000 MHz
Type
Dipole (Ξ»/2)
Ξ»/4Ξ»
Antenna Shape
E-Plane Pattern
βΉ
Design Insights
Select antenna type and enter frequency to see design insights.
Common Applications
Amateur Radio
HF dipoles, VHF/UHF quarter-wave verticals, and half-wave end-fed antennas for ham radio operation.
IoT & Wireless
PCB trace antennas, whip antennas, and wire antennas for WiFi, Bluetooth, Zigbee, LoRa and ISM bands.
Broadcast & FM
Half-wave dipole arrays and quarter-wave ground-plane antennas for FM/AM/DAB broadcast transmitters.
RF Prototyping
Quick antenna sizing for any RF project β from 1 MHz to 10 GHz β during circuit design and testing phases.
Get "10 RF Design Principles Every Engineer Should Know" Free
Learn practical principles for better RF circuits, PCB layouts, simulations, measurements, and troubleshooting.