Wavelength Calculator
Find wavelength from frequency, and identify where it sits on the spectrum.
Please note: Results use idealised models — point masses, no air resistance, ideal gases and uniform materials. Real experiments deviate. Use these for study and estimation, not for engineering sign-off.
What the Wavelength Calculator does
Wavelength is the distance between successive crests, found by dividing the wave speed by the frequency. For electromagnetic waves it also determines where the wave sits on the spectrum — from kilometre-long radio waves to picometre gamma rays.
Formula
λ = v ÷ fFor light in vacuum: λ = c ÷ fc = 299,792,458 m/sPhoton energy E = hf
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Frequency | number | Yes | — |
| Frequency unit | one of 5 options | Yes | — |
| Medium | one of 7 options | Yes | — |
| Wave speed | number | In some modes | Shown Medium is Custom wave speed. |
| Wave speed unit | one of 5 options | In some modes | Shown Medium is Custom wave speed. |
How to use it
- Choose Frequency unit and Medium.
- Enter Frequency.
- Fill in the remaining inputs the form shows for your choice.
- Select Calculate.
Worked example
An FM radio station broadcasting at 100 MHz.
- Frequency
- 100 MHz
- Medium
- Light in vacuum
λ = 299,792,458 ÷ 100,000,000 = 2.998 m — a radio wave. A half-wave antenna for it would be about 1.5 m long.
Frequently asked questions
Does light change colour underwater?
No. Its speed and wavelength both drop, but frequency stays the same, and it is frequency that your eye responds to as colour.
Why are radio antennas sized to the wavelength?
An antenna resonates most strongly when its length matches a half or quarter of the wavelength, which is why a 100 MHz antenna is roughly 1.5 m.