Physics · Waves
Wavelength and frequency calculator.
Pick what to solve for, choose a medium for the wave speed, and enter the other two values. Sound in air adjusts for temperature.
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Result
Enter your values.
Wave speed, frequency and wavelength
Every wave obeys v = f × λ: speed equals frequency times wavelength. OpenStax writes it as v = λ ÷ T = λf. The speed is set by the medium; frequency is set by the source. Light in a vacuum travels at exactly 299,792,458 m/s (NIST). Sound in air at 20 °C is about 331.4 + 0.61 × 20 = 343.6 m/s (HyperPhysics, close to room temperature only).
Worked example. Concert A, 440 Hz, in 20 °C air: λ = 343.6 ÷ 440 = 0.7809 m. A 100 MHz FM radio wave in vacuum: λ = 299,792,458 ÷ 100,000,000 = 2.998 m. A sound wave in 20 °C air with a 1 m wavelength has f = 343.6 Hz.
The solid and liquid speeds in the presets are HyperPhysics table values (from Serway and Beichner) and vary with temperature and material grade. The presets are not for acoustic design or radio engineering.
Frequently asked questions
How do I calculate wavelength from frequency?
λ = v ÷ f. For 440 Hz in 20 °C air that is 0.7809 m.
What speed of sound does the calculator use for air?
v = 331.4 + 0.61 × T in m/s with T in °C, the HyperPhysics approximation for temperatures near room temperature.
What is the wavelength of a 100 MHz radio wave?
2.998 m, using c = 299,792,458 m/s.
Does frequency change when a wave enters a new medium?
No. Frequency is set by the source; speed and wavelength change together.
Can I use my own wave speed?
Yes. Choose Custom wave speed or just type a value into the wave speed box.
Sources
Checked
- OpenStax University Physics Volume 1, 16.2 Mathematics of Waves
- HyperPhysics: Speed of Sound in Air
- HyperPhysics: Speed of Sound in Various Bulk Media
- NIST CODATA: speed of light in vacuum
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Scope
Idealised textbook relation for uniform media. Not for acoustic, radio or safety engineering. Results are arithmetic from the formulas shown, for study and general interest, and not professional or engineering advice.