Tuning Fork Calculator
A tuning fork sounds a single, pure pitch, and that pitch sits in a precise relationship to every other note. This calculator finds the frequency of any note a given number of semitones from concert A using equal temperament, then derives the period of vibration and the wavelength of the sound in air. The reference pitch defaults to the ISO standard of 440 hertz but is editable, as is the speed of sound, which changes with air temperature. Use it to identify fork frequencies, check tuning, or relate pitch to wavelength.
Tuning fork formula
Frequency = reference A4 * 2^(semitones / 12)
Period = 1 / frequency
Wavelength = speed of sound / frequency
Octaves from A4 = semitones / 12
The frequency relation is the equal temperament definition. Period and wavelength are exact physical definitions. The reference pitch and the speed of sound are editable inputs, since tuning standards and air temperature vary.
Pitch and sound facts
- The ISO 16 standard sets concert A at 440 hertz.
- Each octave doubles the frequency; twelve equal semitones span an octave.
- Middle C is nine semitones below A4 in a different octave, around 261.63 hertz.
- The speed of sound in dry air near 20 degrees Celsius is about 343 metres per second.
- Warmer air speeds sound up, lengthening the wavelength of a fixed-frequency tone.
Tuning fork: frequently asked questions
How is a note frequency calculated?
Equal temperament tuning sets each note as the reference pitch times two raised to the number of semitones divided by twelve. With concert A (A4) as the reference, a note n semitones away has frequency A4 times 2 to the power n over 12. Twelve semitones double the frequency, which is one octave.
What is the standard reference pitch?
The international standard is A4 at 440 hertz, defined in ISO 16. Some orchestras tune to 442 or 443 hertz, and historical pitches differ. The reference frequency is an editable input so you can match whatever tuning you use.
What is the period of a tuning fork?
The period is the time for one full vibration, equal to one divided by the frequency. A 440 hertz fork has a period of about 0.00227 seconds, or 2.27 milliseconds. The calculator shows the period in seconds.
How is the wavelength found?
Wavelength is the speed of sound divided by the frequency. In dry air at about 20 degrees Celsius the speed of sound is roughly 343 metres per second, so a 440 hertz tone has a wavelength of about 0.78 metres. The speed of sound is editable because it changes with temperature.
Why does temperature change the wavelength?
The frequency of a vibrating fork is fixed by its physical design, but sound travels faster in warmer air. Since wavelength equals speed divided by frequency, a higher speed of sound at higher temperature gives a longer wavelength for the same note.
Official sources
- International Organization for Standardization: ISO 16 standard tuning frequency.
- National Institute of Standards and Technology: SI units (hertz, metre, second).
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.