C4 has a frequency of approximately 261.63 Hz in twelve-tone equal temperament when A4 is tuned to 440 Hz. More precisely, its fundamental frequency is 261.6256 Hz. C4 is commonly called middle C and corresponds to MIDI note number 60.
The value 261.63 Hz means that a simple C4 tone completes about 261.63 vibration cycles per second. Real voices and instruments also produce harmonics above that fundamental, so a recorded C4 contains more frequencies than 261.63 Hz alone. For a broader reference, see the music note frequency chart.
What Is the Frequency of C4?
The standard C4 frequency is 261.63 Hz when the tuning system uses A4 = 440 Hz and divides each octave into 12 equal semitones. Depending on rounding, the same pitch may be shown as 261.6 Hz, 261.63 Hz, or 261.626 Hz.
Hertz measures cycles per second. A steady fundamental at 261.63 cycles per second should register as C4 under standard tuning, although a voice or acoustic instrument may fluctuate slightly.
Fundamental frequency should not be confused with the full acoustic spectrum. A piano playing C4 has a fundamental near 261.63 Hz plus harmonics around multiples of that value. Those overtones help distinguish the piano from a guitar or voice playing the same note. This distinction is explored further in the guide to pitch and frequency.
Why Is C4 Called Middle C?
C4 is called middle C because of its central role in keyboard layout and musical notation. On an 88-key piano, it is the fourth C from the left and sits near the physical center of the keyboard, although it is not the instrument’s exact middle key.
Where C4 sits on a piano
Middle C is the white key immediately to the left of the group of two black keys near the keyboard’s center. Its MIDI note number is 60, which provides a consistent digital identifier even when software uses a different octave-labeling convention.
On the grand staff, middle C is written on a short ledger line between the bass and treble staves. That position makes it a useful reference point for both hands in piano notation. A more detailed keyboard comparison appears in the piano note frequency reference.
What “middle” does not mean
The word “middle” does not mean C4 is the midpoint of human hearing. Human hearing covers a much wider logarithmic range, commonly described as roughly 20 Hz to 20,000 Hz for young listeners with healthy hearing.
Middle C is also not the frequency midpoint of a piano. Frequency rises exponentially rather than by equal additions.
How Is the C4 Frequency Calculated?
C4 is calculated from the A4 = 440 Hz reference using the twelve-tone equal-temperament formula. C4 is nine semitones below A4, so its frequency is:
[
f = 440 \times 2^{-9/12}
]
[
f \approx 261.6256\text{ Hz}
]
The general MIDI-based form is:
[
f = 440 \times 2^{(n-69)/12}
]
Here, (n) is the MIDI note number. Substituting 60 for C4 gives:
[
440 \times 2^{(60-69)/12} \approx 261.6256\text{ Hz}
]
Each semitone multiplies frequency by (2^{1/12}), while moving up one complete octave doubles frequency. The A4 frequency explanation shows why 440 Hz serves as the starting reference for these calculations.
How Does C4 Compare With Nearby Notes and Octaves?
C4 sits between B3 and C♯4/D♭4. In standard equal temperament, the neighboring pitches are separated by one semitone.
| Note | MIDI number | Frequency |
|---|---|---|
| B3 | 59 | 246.94 Hz |
| C4 | 60 | 261.63 Hz |
| C♯4/D♭4 | 61 | 277.18 Hz |
Every C one octave above has twice the previous frequency, and every C one octave below has half of it.
| Note | Frequency under A4 = 440 Hz |
| C2 | 65.41 Hz |
| C3 | 130.81 Hz |
| C4 | 261.63 Hz |
| C5 | 523.25 Hz |
| C6 | 1046.50 Hz |
This doubling relationship is the defining acoustic feature of an octave. Two notes an octave apart share the same letter name and are strongly related perceptually, even though the higher note vibrates twice as fast. The guide to how octaves work explains the relationship in greater depth.
At an approximate sound speed of 343 metres per second, a 261.63 Hz tone has a wavelength of about 1.31 metres:
[
\lambda = \frac{343}{261.63} \approx 1.31\text{ m}
]
Frequency describes how often the wave repeats, while wavelength describes the physical distance between corresponding points in the wave.
Is C4 Always 261.63 Hz?
C4 is not always exactly 261.63 Hz. That figure depends on the reference pitch A4 = 440 Hz and twelve-tone equal temperament. If an ensemble adopts a different concert pitch, all notes—including C4—shift proportionally.
| A4 reference | Equal-tempered C4 |
| 432 Hz | 256.87 Hz |
| 440 Hz | 261.63 Hz |
| 442 Hz | 262.81 Hz |
| 443 Hz | 263.41 Hz |
An orchestra tuning A4 to 442 Hz produces a slightly higher C4 than an ensemble using A440. The note name stays C4, but its measured frequency changes. The article on concert pitch standards explains why groups must agree on a reference.
Just intonation, meantone temperament, and historical temperaments can also place C differently relative to A. Therefore, 261.63 Hz is a modern standard value, not a universal value.
Is C4 the Same as 256 Hz?
C4 is about 261.63 Hz in modern A440 equal temperament, while 256 Hz refers to a different historical tuning concept sometimes called scientific pitch. The two values should not be treated as interchangeable.
Scientific pitch set middle C to 256 Hz because 256 is a power of two, making octave calculations convenient. Its A above middle C is approximately 430.54 Hz.
The similar terms cause confusion: scientific pitch notation is the naming system in which middle C is called C4, while scientific pitch is a tuning proposal that assigns middle C a frequency of 256 Hz. Learning the rules of scientific pitch notation helps keep the label separate from the tuning standard.
Why Might Software Label Middle C as C3 or C5?
Music software may label MIDI note 60 as C3, C4, or C5 because there is no universally followed octave-numbering display convention across every digital audio workstation, keyboard, and manufacturer. The physical pitch can remain identical even when the displayed octave number changes.
MIDI note 60 is the most reliable cross-system identifier for middle C. If two programs disagree about whether it is C3 or C4, check the MIDI number or measured frequency. A tone near 261.63 Hz under A440 is the same pitch regardless of the label shown on screen.
How Can You Measure or Match C4?
You can measure C4 with a chromatic tuner, frequency analyzer, or pitch detector. Play or sing a steady tone, keep the microphone at a consistent distance, and look for a reading near 261.63 Hz or MIDI note 60.
Microphone-based measurements are estimates. Noise, room reflections, vibrato, breathiness, and overtones can move the reading. A tuner may display an overtone or neighboring note if the fundamental is weak.
When matching C4 by voice, use a comfortable volume and avoid forcing the note if it lies outside your easy range. Start from a nearby comfortable pitch and move by small steps. The practical guide to singing on pitch covers listening and adjustment techniques that make matching a reference tone more reliable.
Frequently Asked Questions
Is C4 always 261.63 Hz?
No. C4 is approximately 261.63 Hz in twelve-tone equal temperament with A4 set to 440 Hz. A different reference pitch or tuning system can assign C4 a slightly different frequency.
Is C4 the same note as middle C?
Yes, C4 is the standard scientific-pitch-notation label for middle C. It is also MIDI note 60, although some software displays that same pitch as C3 or C5.
Is middle C 256 Hz or 261.63 Hz?
Middle C is approximately 261.63 Hz under modern A440 equal temperament. The 256 Hz value belongs to the historical scientific-pitch tuning system.
What are the frequencies of C3 and C5?
Under A4 = 440 Hz tuning, C3 is approximately 130.81 Hz and C5 is approximately 523.25 Hz. C3 is half the frequency of C4, while C5 is twice its frequency.
Why does some music software call middle C C3?
Software developers and hardware manufacturers use different octave-numbering conventions. Check for MIDI note 60 or a frequency near 261.63 Hz to identify middle C regardless of the displayed octave label.
What MIDI note number is C4?
C4 is MIDI note number 60 under the commonly used scientific pitch notation convention. MIDI 60 identifies the same key and pitch even when a program assigns it a different octave name.
Vincent is a pitch detection and vocal analysis writer at OnlinePitchDetector. He focuses on pitch recognition, vocal frequency analysis, singing tools, and real-time audio testing for singers, musicians, producers, and beginners.