# Dipole Antenna Calculator

URL: https://speedycalculator.com/calculators/physics/dipole/
Last updated: 2026-10-30

> The dipole antenna calculator finds the total length and leg length of a half-wave dipole for a given frequency, including the end-effect (velocity) factor, and the wavelength.

## Inputs

- Frequency f (MHz, kHz, GHz)
- End-effect (shortening) factor K

## Results

- Wavelength λ
- Total dipole length
- Length of each leg

## Formula

```
λ = c/f,  L_total = K·λ/2,  leg = L_total/2  (K ≈ 0.95 for wire; L(ft) ≈ 468/f(MHz))
```

## Explanation

The half-wave dipole is the simplest practical antenna – two wires fed in the middle. Its resonant length is slightly shorter than half a wavelength because of end effects, which is why amateur radio operators use the famous 468/f rule.

### How to use the Dipole Antenna Calculator

- **Frequency f**
- **End-effect (shortening) factor K**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the frequency and the end-effect factor (0.95 for thin wire; lower for thick conductors).

### Inputs explained

FieldWhat to enterFrequency fUnits: MHz, kHz, GHzEnd-effect (shortening) factor KA number

### What each result means

- **Wavelength λ** = 299792458÷[Frequency f]
- **Total dipole length** = [End-effect (shortening) factor K]×299792458÷[Frequency f]÷2
- **Length of each leg** = [End-effect (shortening) factor K]×299792458÷[Frequency f]÷4

### Example values

How the main result changes when **Frequency f** changes and everything else stays at the example values above:

Frequency f (MHz)Total dipole length (m)7.120.056510.6513.37114.210.028317.758.022621.36.685528.45.0141

## Worked example

Inputs — Frequency f: 14.2 MHz; End-effect (shortening) factor K: 0.95.

Results — Wavelength λ = 21.11214 m; **Total dipole length = 10.02827 m**; Length of each leg = 5.01413 m.

## Key terms

- **Half-wave dipole**: Antenna about half a wavelength long.

## FAQ

**What is the 468 rule?**
Total length in feet ≈ 468 / frequency in MHz.

**Why is the dipole shorter than λ/2?**
End effects and conductor thickness lower the resonant frequency.

**What is the feed-point impedance?**
About 73 Ω in free space, lower near the ground.

**How do I tune it?**
Trim the ends equally until the SWR is lowest at your frequency.


## Sources

- [OpenStax – University Physics Volume 2](https://openstax.org/details/books/university-physics-volume-2)
- [HyperPhysics (Georgia State University)](http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)