Antenna length calculator
Cut an antenna to the right size for any frequency. From the wavelength λ = c/f and a velocity factor, it sizes a half-wave dipole, quarter-wave vertical, 5/8-wave vertical or full-wave loop, returning the total length and the per-element length in both metres and feet.
Related tools
All Electronics tools →The Antenna length calculator turns Frequency, Frequency unit, Antenna type, Velocity factor K (1 = free space) into Wavelength λ, Total antenna length, Total antenna length, Per element (leg / side / radiator), Per element, instantly and for free. For instance, with Frequency = 100, Frequency unit = kHz, Antenna type = Half-wave dipole (λ/2) and Velocity factor K (1 = free space) = 0.95 it returns Wavelength λ = 2,998 m, Total antenna length = 1,424 m and Total antenna length = 4,672 ft.
How to use it
- Enter your values: Frequency, Frequency unit, Antenna type, Velocity factor K (1 = free space).
- Read the result instantly: Wavelength λ, Total antenna length, Total antenna length, Per element (leg / side / radiator), Per element.
Frequently asked questions
What does the Antenna length calculator actually compute?
It takes Frequency, Frequency unit, Antenna type and Velocity factor K (1 = free space) and derives Wavelength λ, Total antenna length, Total antenna length, Per element (leg / side / radiator) and Per element from them. The calculation is live as you type, so the result updates on every change.
What information do I need to provide?
4 values: Frequency, Frequency unit, Antenna type and Velocity factor K (1 = free space). Nothing else is required — no account, no file upload.
Can you show a worked example?
With Frequency = 100, Frequency unit = kHz, Antenna type = Half-wave dipole (λ/2) and Velocity factor K (1 = free space) = 0.95, the calculator returns Wavelength λ = 2,998 m, Total antenna length = 1,424 m and Total antenna length = 4,672 ft. Those figures come from running this exact tool, so you can reproduce them by entering the same values.
What happens if I enter larger values?
It moves a lot. Using Frequency = 200, Frequency unit = MHz, Antenna type = Quarter-wave vertical (λ/4) and Velocity factor K (1 = free space) = 1.9 instead, Wavelength λ goes from 2,998 m to 1.499 m — which is why it is worth testing a few scenarios rather than trusting a single figure.
Which “Frequency unit” option should I choose?
You can pick between « kHz », « MHz » and « GHz ». Each one changes what the calculator works out, so switch and compare — the default is « kHz ».
When would I actually use this?
At the bench: sizing a resistor for an LED, reading a colour band, working out a divider ratio, and checking a part will not cook.
What is the most common mistake?
Choosing a resistance and forgetting the power rating. A value that is electrically right will still burn if the package cannot dissipate what passes through it — check the watts as well as the ohms.
How accurate is it, and what are the limits?
A dipole splits into two equal legs; a vertical and a loop are single radiators (loop "per element" is one side of a square loop). Velocity factor K accounts for the wire's insulation and end effects — bare wire ≈ 0.95–0.98, coax elements lower. Trim to resonance with an analyser.
What is the difference between the Antenna length calculator and the 555 timer calculator (astable & monostable)?
This one returns Wavelength λ and Total antenna length; the 555 timer calculator (astable & monostable) returns Output frequency (astable) and Output HIGH time. That is the whole difference — open the one whose figure you need.
Is there a tool for the next step?
Impedance calculator (RLC) is the closest one after this: Compute the impedance of a series or parallel RLC circuit at any frequency. From R, L, C and f it returns the inductive and capacitive reactances, the impedance magnitude |Z|, the phase angle and the resonant frequency where the reactances cancel.