Musical Note Frequency Converter
Convert any musical note (C0–B9) to its frequency in Hz, or find the nearest note for any frequency, including the detune in cents. Uses equal temperament with an adjustable A4 reference pitch.
Convert Between Notes and Frequencies
Note Frequency Formula
Frequently Asked Questions
How do I calculate a note's frequency by hand?
Use the equal temperament formula \( f = A4 \times 2^{n/12} \), where \(n\) is the number of semitones between your note and A4. Example: A5 is one octave (12 semitones) above A4, so with A4 = 440 Hz you get \( 440 \times 2^{12/12} = 880 \) Hz. For notes below A4, \(n\) is negative, e.g. A3 = 220 Hz.
What is a normal A4 reference pitch, and when should I change it?
The modern standard is 440 Hz, used by most orchestras and tuners. Historically, A4 varied widely from about 415 Hz (baroque pitch, roughly a semitone lower) to 466 Hz (Renaissance pitch). Some orchestras tune to 442–444 Hz for a brighter sound. If you play with others, always match their reference pitch, otherwise you will sound out of tune together.
What are cents, and how many cents are audible?
A cent is 1/100 of a semitone, so an octave contains 1200 cents. Most people can detect a deviation of about 5–10 cents on sustained notes; trained ears can notice 2–3 cents. Tuning within ±3 cents of the nearest note is generally considered in tune for most instruments.
Why do I get a result like 'A♯ +12 cents' instead of an exact note?
Most real-world frequencies don't land exactly on an equal temperament note, so the converter reports the nearest note plus the detune in cents. A deviation of ±50 cents means the sound sits halfway between two notes. Instruments with just intonation or pure harmonics (bells, wind overtones) often produce frequencies noticeably off the tempered grid.
How do I convert between frequencies and wavelengths or MIDI numbers?
Wavelength in air is \( \lambda = v / f \), where \( v \approx 343 \) m/s at 20 °C. For example, 440 Hz has a wavelength of about 0.78 m. For MIDI, the note number equals \( n = 69 + 12 \log_2(f / A4) \), rounded to the nearest integer — the same formula this calculator uses internally for frequency-to-note conversion.
Why does each octave double the frequency instead of adding a fixed amount?
Pitch perception is logarithmic: going up one octave always doubles the frequency. That's why A4 = 440 Hz, A5 = 880 Hz, and A3 = 220 Hz. Equal temperament then divides each octave into 12 equal ratios, so every semitone multiplies the frequency by \( 2^{1/12} \approx 1.0595 \) — about a 5.95% increase, not a fixed number of Hz.
My instrument tuner shows a different note for the same frequency. Why?
Check the reference pitch first — if the tuner uses A4 = 442 Hz and the calculator uses 440 Hz, every note shifts slightly. Also, some instruments (piano strings, for example) are tuned with stretched octaves, where high notes are slightly sharp and low notes slightly flat compared to pure equal temperament, so deviations of several cents at the extremes are normal.