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Frequency to Note Converter

Convert any frequency in Hertz (Hz) to its corresponding musical note. Get the note name, octave, cents deviation, and exact pitch information.

A4

440.00 Hz

Note:
A
Octave:
4
Cents:
0.00
Exact Freq:
440.00 Hz

This frequency is exactly at A4 (perfectly in tune).

Cents Deviation
-50¢ (Flat) 0¢ +50¢ (Sharp)

The Formula

The conversion from frequency to note uses the following formulas:

Semitones from A4:
n = 12 × log₂(f / 440)

Where f is the frequency in Hz and n is the number of semitones from A4.

Cents Deviation:
cents = 1200 × log₂(f / f_note)

Where f is the input frequency and f_note is the exact frequency of the nearest note.

Understanding Cents

  • There are 100 cents in one semitone
  • 0 cents = perfectly in tune
  • Negative cents = flat (below the note)
  • Positive cents = sharp (above the note)
  • Most people can't hear differences smaller than 5-10 cents

Common Note Frequencies

Note Frequency (Hz) Note Frequency (Hz)
C4 (Middle C) 261.63 C5 523.25
D4 293.66 D5 587.33
E4 329.63 E5 659.25
F4 349.23 F5 698.46
G4 392.00 G5 783.99
A4 440.00 A5 880.00
B4 493.88 B5 987.77

Frequently Asked Questions

Middle C (C4) is approximately 261.63 Hz when using standard A4 = 440 Hz tuning. This is the C note located near the middle of a standard 88-key piano.

A4 = 440 Hz was adopted as the international standard (ISO 16) in 1955. Before this, there was significant variation in tuning standards across different countries and time periods. 440 Hz was chosen as a compromise that was already in common use.

Each octave represents a doubling of frequency. For example, A4 = 440 Hz, A5 = 880 Hz (double), and A3 = 220 Hz (half). This 2:1 ratio is consistent across all notes and is why octaves sound so harmonically related.