Frequency (Hz): The number of vibrations per second that produce the pitch. A4 = 440 Hz is the standard tuning reference. Each octave doubles the frequency, so A5 = 880 Hz.
Note name: The nearest note in 12-tone equal temperament. In frequency-to-note mode, this is the closest named pitch to your input frequency.
Cents offset: How far the pitch is from the nearest equal-tempered note, measured in hundredths of a semitone. ±0 means perfectly in tune; ±50 cents means exactly halfway between two notes.
Wavelength: The physical length of one cycle of the sound wave in air at room temperature (~343 m/s). Lower notes have longer wavelengths — useful for understanding room acoustics and speaker placement.
How This Calculator Works
You pick a note and octave (or enter a frequency) and the tool applies the 12-tone equal temperament formula: f = 440 × 2^((MIDI − 69) / 12), where MIDI maps every semitone to an integer. An optional cents offset fine-tunes the result by multiplying by 2^(cents / 1200). Wavelength is computed as the speed of sound in air (343 m/s) divided by the frequency. It assumes A4 = 440 Hz standard concert pitch.
Quick Questions
Why is A4 set to 440 Hz?
440 Hz became the international standard (ISO 16) in 1955 and is used by most orchestras, manufacturers, and digital tuners worldwide. Some ensembles tune slightly higher (441–443 Hz) for a brighter sound, and historically A4 ranged from 415 to 466 Hz.
What is equal temperament?
Equal temperament divides the octave into 12 equal semitones, each a frequency ratio of 2^(1/12) ≈ 1.05946. This makes every key sound equally in-tune (or equally slightly out-of-tune), which is why pianos and guitars use it.
What are cents used for?
Cents measure small pitch differences — 100 cents equals one semitone. Tuners display cents to show how sharp or flat a note is. String players and vocalists use cents to evaluate intonation precision.
How accurate is the wavelength?
The wavelength assumes sound travels at 343 m/s (20°C dry air). Temperature, humidity, and altitude affect the speed of sound, so the actual wavelength may vary by a few percent in different conditions.