Case 1
- Frequency
- 100000000Hz
2.997925m
Open with these valuesWavelength Calculator
2.997925m
Result: 2.997925 mWavelength is the speed of light divided by the frequency, so 100 MHz gives about 3 m and 2.4 GHz about 12.5 cm. Doubling the frequency always halves the wavelength. The value used here is the vacuum speed; inside glass or water the wave is shorter.
Worked examples
Case 2
- Frequency
- 2400000000Hz
0.124914m
Open with these valuesCase 3
- Frequency
- 1000000Hz
299.792458m
Open with these valuesHow it's calculated
λ = c ÷ f
- StepEnter the frequency in hertz — 100 MHz is 100000000, 2.4 GHz is 2400000000.
- StepRead the wavelength in metres.
- ResultFor a half-wave antenna, halve that length.
Reference table
| Frequency in Hz | Band | Wavelength in m |
|---|---|---|
| 1 | One cycle per second | 299792458 |
| 1000000 | 1 MHz, medium wave radio | 299.792458 |
| 100000000 | 100 MHz, FM radio | 2.997925 |
| 2400000000 | 2.4 GHz, Wi-Fi and microwaves | 0.124914 |
Questions
How is wavelength calculated?
Divide the speed of light by the frequency. With c = 299792458 m/s, a 100 MHz radio wave spans 299792458 ÷ 100000000 = 2.997925 m, near enough 3 m.
Why does the formula use the speed of light?
Radio, microwaves and visible light are all electromagnetic waves and travel at the same fixed speed in vacuum, so wavelength and frequency are locked together. For sound you would swap in the speed of sound, around 343 m/s in air, because sound is mechanical rather than electromagnetic.
How does frequency affect wavelength?
They are inversely related, because their product is the fixed speed of light. FM radio near 100 MHz spans about 3 m, Wi-Fi at 2.4 GHz only 12.5 cm, and visible light a few hundred nanometres. Doubling the frequency always halves the wavelength.
What is the period, and where is it?
The period is the time one cycle takes, simply 1 divided by the frequency — a 100 MHz wave has a period of 10 nanoseconds. This calculator reports the wavelength, the distance one cycle spans, because that is the figure antennas and optics are sized against.
Does the wavelength change inside glass or water?
Yes. The frequency stays put, but light travels slower in a medium, so the wavelength shrinks by the refractive index. In water at 1.33 a 500 nm wave measures about 376 nm.
Sources and last check
Information, not professional advice.