Calculator
Find wave frequency from wavelength using f = v / λ. Use vacuum speed for electromagnetic waves, or enter a custom wave speed for other media.
What is frequency from wavelength?
Frequency tells you how many wave cycles pass a point each second, measured in hertz (Hz). Wavelength is the physical length of one cycle of the wave, measured in meters (or converted from units like nm, cm, or km). If you know the wavelength and wave speed, you can calculate frequency immediately.
For electromagnetic waves (radio, microwave, infrared, visible light, ultraviolet, X-rays), the speed in vacuum is the speed of light. For mechanical waves (like sound), the wave speed depends heavily on the medium.
Frequency of wavelength formula
- f = v / λ
- f = frequency (Hz)
- v = wave speed (m/s)
- λ = wavelength (m)
If your wavelength is in nanometers, micrometers, centimeters, or other units, convert it to meters first. This calculator performs that conversion automatically.
How to use this calculator
Step-by-step
- Enter a wavelength value.
- Select its unit (m, cm, mm, µm, nm, Å, or km).
- Choose a speed preset (vacuum, air, water, glass) or custom speed.
- Click Calculate Frequency.
The result panel returns frequency in Hz, a compact SI form (kHz/MHz/GHz/THz...), period, and wavelength converted to meters.
Worked examples
Example 1: Green laser light at 532 nm
In vacuum, v = 299,792,458 m/s and λ = 532 nm = 5.32 × 10-7 m. Frequency is roughly 5.64 × 1014 Hz (about 563.5 THz).
Example 2: Radio wave with 3 m wavelength
In vacuum, f = 299,792,458 / 3 ≈ 99,930,819 Hz (about 99.93 MHz).
Example 3: Wave in water with custom speed
If λ = 2 m and v = 1,500 m/s (typical sound speed in water), then f = 1,500 / 2 = 750 Hz.
Quick wavelength conversion reference
| Unit | Equals in meters |
|---|---|
| 1 km | 1,000 m |
| 1 cm | 1 × 10-2 m |
| 1 mm | 1 × 10-3 m |
| 1 µm | 1 × 10-6 m |
| 1 nm | 1 × 10-9 m |
| 1 Å | 1 × 10-10 m |
Common mistakes to avoid
- Entering wavelength in nm but treating it as meters.
- Using speed of light for sound calculations.
- Forgetting frequency is inversely proportional to wavelength (shorter λ means higher f).
- Mixing unit systems without converting first.
FAQ
Does this work for all waves?
Yes. The same core equation works for electromagnetic and mechanical waves, as long as the wave speed is appropriate for the medium.
What happens when wavelength decreases?
Frequency increases if speed is constant, because frequency and wavelength have an inverse relationship.
Can I use this as a light frequency calculator?
Absolutely. Keep the preset on vacuum (or air) and enter your wavelength in nm for quick visible-spectrum calculations.