Wavelength to Frequency Calculator – Free λ to Hz Converter
Wavelength & Frequency Calculator
Free wavelength to frequency calculator – determine the wavelength, frequency, or wave speed using standard physics formulas (v = λ × f).
Use this free wavelength to frequency calculator to convert λ to Hz, Hz to λ, or find wave speed for light, radio and sound waves.
Quick answer
A wavelength to frequency calculator uses the wave equation f = v ÷ λ. For light and radio waves, v is the speed of light (299,792,458 m/s); for sound in air at 20°C it is about 343 m/s. Example: a 0.125 m wavelength gives 299,792,458 ÷ 0.125 ≈ 2.4 GHz (Wi-Fi). Enter any two values and the tool solves the third instantly.
Table of Contents
Our free wavelength to frequency calculator converts wavelength (λ) to frequency (f), frequency to wavelength, or finds the wave speed (v) when you know the other two. It is built for physics students, radio amateurs, antenna builders, audio engineers and anyone working with light or sound waves.
One click loads the speed of light or the speed of sound, the active formula is shown step by step with your numbers, and a built-in reference table lists common waves such as Wi-Fi, FM radio and visible light. Everything runs in your browser – nothing is uploaded.
Wavelength to Frequency Formula
Every wave obeys the same relationship between speed, wavelength and frequency:
- Frequency: f = v ÷ λ
- Wavelength: λ = v ÷ f
- Wave speed: v = λ × f
Here f is in hertz (Hz), λ is in metres (m) and v is in metres per second (m/s). For electromagnetic waves in a vacuum – light, radio, microwaves, X-rays – v is the speed of light, c = 299,792,458 m/s. In air it is only about 0.03% slower, so c is used for almost all practical radio work.
Worked example: wavelength to frequency
Red light has a wavelength of about 700 nm (0.0000007 m). f = 299,792,458 ÷ 0.0000007 ≈ 4.28 × 1014 Hz, or about 428 THz.
Worked example: frequency to wavelength
An FM station broadcasting at 100 MHz (100,000,000 Hz) has λ = 299,792,458 ÷ 100,000,000 ≈ 3 m. A quarter-wave antenna for that station is therefore about 75 cm long.
Worked example: sound waves
The musical note A4 is 440 Hz. In air at 20°C, λ = 343 ÷ 440 ≈ 0.78 m. Click the Speed of Sound preset to use 343 m/s automatically.
How to Use the Wavelength to Frequency Calculator
Convert between wavelength and frequency in three quick steps.
Step 1: Choose the Wave Speed
Click Speed of Light (Vacuum) for light, radio and microwaves, or Speed of Sound (Air) for audio. You can also type any custom wave speed in m/s, for example sound in water (about 1,480 m/s).
Step 2: Enter the Wavelength or Frequency
Type the wavelength in metres to get frequency, or type the frequency in hertz to get wavelength. Fill any two of the three fields and the third is solved instantly. Use decimals or scientific values, e.g. 0.125 m or 2400000000 Hz.
Step 3: Read the Formula and Copy Results
The Active Physics Formula box shows the exact calculation with your numbers, such as 299792458 m/s ÷ 0.125 m = 2.3983e+9 Hz. Click Copy Results to copy the answer, or Clear Fields to start again. The reference table below gives quick values for common waves.
Common Wavelength and Frequency Values
| Wave | Frequency | Wavelength |
|---|---|---|
| AM radio | 1 MHz | ≈ 300 m |
| FM radio | 100 MHz | ≈ 3 m |
| Wi-Fi 2.4 GHz | 2.4 GHz | ≈ 12.5 cm |
| Wi-Fi 5 GHz | 5 GHz | ≈ 6 cm |
| Microwave oven | 2.45 GHz | ≈ 12.2 cm |
| Red light | ≈ 428 THz | ≈ 700 nm |
| Blue light | ≈ 666 THz | ≈ 450 nm |
| Sound, note A4 (air) | 440 Hz | ≈ 78 cm |
Unit Tips for Accurate Results
The wavelength to frequency calculator works in base SI units, so convert first:
- 1 nm = 0.000000001 m (10−9 m); 1 cm = 0.01 m; 1 mm = 0.001 m
- 1 kHz = 1,000 Hz; 1 MHz = 106 Hz; 1 GHz = 109 Hz; 1 THz = 1012 Hz
- Very large or small answers are shown in scientific notation – 2.3983e+9 means 2.3983 × 109
Frequency and wavelength are inversely proportional: double the frequency and the wavelength halves. That is why high-frequency 5 GHz Wi-Fi uses shorter waves than 2.4 GHz and does not pass through walls as well.
Who Uses a Wavelength to Frequency Calculator?
- Students checking physics homework on the wave equation and the electromagnetic spectrum.
- Radio amateurs and antenna builders sizing dipoles and quarter-wave antennas.
- Network engineers planning Wi-Fi and 5G channels.
- Audio engineers working out room modes and speaker placement.
- Optics and lab work converting laser wavelengths in nm to THz.
Working with other physics or engineering units? Try our Torque Unit Converter or solve matrix problems with the Eigenvalue & Eigenvector Calculator.
Frequently Asked Questions
How do you convert wavelength to frequency?
Divide the wave speed by the wavelength: f = v ÷ λ. For light and radio use 299,792,458 m/s; for sound in air use about 343 m/s.
What is the frequency of a 1 metre wavelength?
For an electromagnetic wave, 299,792,458 ÷ 1 ≈ 300 MHz. For sound in air it is about 343 Hz.
Are wavelength and frequency inversely proportional?
Yes. At a fixed wave speed, a higher frequency always means a shorter wavelength, and vice versa.
What units does the calculator use?
Metres for wavelength, hertz for frequency and metres per second for speed. Convert nm, MHz or GHz to base units first.
Can I use it for sound waves?
Yes. Click Speed of Sound (Air) to load 343 m/s, or enter a custom speed for water or other materials.
Is the wavelength to frequency calculator free?
Yes. It is completely free, needs no sign-up and runs entirely in your browser.