To convert hertz to a note, count the semitones between the frequency and A4 = 440 Hz: 12 × log2(f / 440). The nearest whole number is the note, and the remainder tells you how many cents sharp or flat it is. To find the pitch of a voice, sing or speak a steady vowel into a tuner, read the frequency of its fundamental and convert it.
In Short
The short version:
- A4 = 440 Hz is the reference; an octave doubles the frequency.
- One semitone is a factor of about 1.0595; 100 cents make a semitone.
- Middle C is C4 = 261.63 Hz.
- Typical speaking voices: about 85–155 Hz for men, 165–255 Hz for women.
- Measure a held vowel, not running speech.
The Reference: A4 = 440 Hz
A frequency only becomes a note name once a reference has been agreed. Today that reference is A4, the A above middle C, at 440 Hz. The International Organization for Standardization adopted it in 1955 and published it as ISO 16 in 1975; before that, orchestras and countries used a range of values. Some orchestras still tune slightly higher, at 442 or 443 Hz.
From this one anchor every other note follows, because the system used in Western music, equal temperament, spaces the notes evenly: each of the twelve semitones in an octave multiplies the frequency by the twelfth root of 2, about 1.0595, and twelve of them double it.
The Formula: From Hertz to a Note
The number of semitones n between a frequency f and A4 is n = 12 × log2(f / 440). Round n to the nearest whole number and count that many semitones up from A4 (or down, if the number is negative) to find the note. The part you rounded away, multiplied by 100, is the deviation in cents.
An example: a voice holds a tone at 196 Hz. 12 × log2(196 / 440) = -14.0, so the note lies 14 semitones below A4, which is G3. A tone at 200 Hz gives -13.65: the nearest note is still G3, and the remaining 0.35 semitones mean that it is 35 cents sharp.
You do not have to do this by hand: the Frequency to Note Converter gives the note, the cents and the exact frequency of the note, and lets you hear it.
Octave Numbers: Which C Is C4?
A note name alone is ambiguous, because there is an A in every octave. Scientific pitch notation, the system used by audio software, adds a number: the octave changes at every C, middle C is C4 and the A above it is A4. An older system, Helmholtz notation, uses capital and small letters with strokes instead, so that middle C is written c′ and A4 is a′. One trap: some MIDI software numbers the octaves one lower and calls middle C C3, so check which convention a program uses.
Typical Voice Ranges in Hz and Notes
Voices differ, but most fall into predictable regions. The values below are typical figures; individual voices vary, and so do the figures given by different sources.
| Voice | Fundamental frequency | Notes |
|---|---|---|
| Adult male, speaking | about 85–155 Hz | F2 to D♯3 |
| Adult female, speaking | about 165–255 Hz | E3 to C4 |
| Bass, singing | about 82–330 Hz | E2 to E4 |
| Tenor, singing | about 131–523 Hz | C3 to C5 |
| Alto, singing | about 175–698 Hz | F3 to F5 |
| Soprano, singing | about 262–1047 Hz | C4 to C6 |
The fundamental is only the lowest part of a voice. Its harmonics and resonances reach far higher, which is why a voice needs the range up to several kilohertz to sound clear. How the voice produces its pitch and its tone is explained in What Is Audio Pitch?.
How to Find the Pitch of a Voice
You need a way to read the frequency, and then the conversion.
Step 1: Hold a Steady Vowel
Speech glides up and down all the time, so there is no single frequency to read. Sing or speak a long, even “ah” at a comfortable level instead.
Step 2: Read the Fundamental Frequency
Use a tuner app or the spectrum display of an audio program. The fundamental is the lowest strong peak; the peaks above it, at two, three and four times that frequency, are its harmonics.
Step 3: Convert It to a Note
Type the frequency into the Frequency to Note Converter. It shows the nearest note and how many cents above or below it your voice is. Press Play Tone to compare the tone with your voice.
Step 4: Use the Result
Knowing the note, you can choose a key that suits the voice, or move a backing track by the right number of semitones with the Pitch & Speed Changer.
Where Hz-to-Note Conversion Helps
- Tuning drums and bass: a kick or an 808 that rings at 49 Hz is a G1. If the song is in A, tuning it to 55 Hz (A1) makes the low end sit together.
- Hunting resonances: when an EQ sweep finds a ringing tone at 392 Hz, the converter tells you it is G4, which helps you judge whether it belongs to the music or to the room.
- Choosing a key: once you know the lowest and the highest note you can sing comfortably, you can pick or transpose songs to fit. The BPM & Key Analyzer finds the key of an existing song.
Convert a Frequency Now
Type a value in hertz and see the note, the cents and the exact frequency.
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