Hz to Note Converter
Convert frequency to the nearest musical note, cents deviation, MIDI note, and exact equal-tempered target frequency.
440.000 Hz • MIDI 69 • 0.00 cents
Centered on the nearest equal-tempered note.
A4 • MIDI 69 • A4 reference 440.0 Hz
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Calculation basis
This converter assumes 12-tone equal temperament. A4 defaults to 440 Hz, and changing the A4 reference shifts all note frequencies proportionally while preserving equal semitone spacing.
Cents interpretation
Zero cents means the entered frequency matches the nearest calculated note. Negative values are flat; positive values are sharp. One equal-tempered semitone equals 100 cents.
Privacy
All conversion math runs locally in your browser. No microphone access, audio upload, or account is required.
The Hz to Note Converter turns a frequency in Hertz into the nearest musical note, octave, MIDI note number, exact target frequency, and cents deviation. It is useful for musicians, producers, instrument technicians, audio developers, and anyone working with measured pitch or frequency data.
Enter a frequency such as 440 Hz and the converter immediately identifies the closest equal-tempered note. You can also change the A4 reference pitch, choose whether accidentals appear as sharps or flats, inspect neighboring notes, and convert a musical note back into its exact frequency.
If you need to detect pitch directly from live audio instead of entering a known frequency, use the Pitch Detector. For broader frequency calculations, the Frequency Calculator provides additional conversion options.
How to Use the Hz to Note Converter
Start in Hz → Note mode and enter the frequency you want to analyze.
For example:
440 Hz
With the default A4 reference of 440 Hz, the result is:
- Note: A4
- MIDI note: 69
- Target frequency: 440 Hz
- Cents deviation: 0
- Status: In tune
The converter updates instantly as the frequency changes.
You can also choose whether black-key notes are displayed using sharps or flats. A pitch might therefore appear as either C♯4 or D♭4 depending on your preference. The underlying frequency does not change.
The A4 reference pitch can also be adjusted. The default is 440 Hz, but presets such as 432 Hz, 442 Hz, and 443 Hz are available for workflows that use a different concert-pitch reference.
How Hertz Is Converted to a Musical Note
Musical pitch frequencies are logarithmic rather than evenly spaced in Hertz.
In 12-tone equal temperament, each octave contains 12 equally spaced semitones. Moving up one octave doubles the frequency.
For example:
- A3 = 220 Hz
- A4 = 440 Hz
- A5 = 880 Hz
The converter determines how many equal-tempered semitone steps the input frequency is from the selected A4 reference, then chooses the nearest note.
The underlying relationship can be expressed as:
Semitone distance = 12 × log₂(frequency ÷ A4 reference)
Once the nearest semitone is identified, the converter can determine the note name, octave, MIDI number, and exact target frequency.
This is a different type of calculation from musical timing. If you need to convert BPM into milliseconds or rhythmic note durations instead, use the Delay Time Calculator.
Understanding Note Names and Octaves
The result uses scientific pitch notation, where a note name is followed by its octave number.
Examples include:
- C3
- G3
- A4
- C5
- F♯5
The octave number helps distinguish notes with the same letter name at different frequencies.
A4 is the A above middle C and is commonly used as a reference tuning pitch. With A4 set to 440 Hz, middle C—C4—is approximately 261.626 Hz.
The converter also shows the previous and next semitone around the nearest result. This makes it easier to see how the entered frequency relates to neighboring pitches rather than viewing one note in isolation.
What Cents Deviation Means
A frequency will not always land exactly on an equal-tempered note.
The converter therefore shows cents deviation, which measures how far the frequency is above or below the nearest note.
One equal-tempered semitone contains 100 cents.
The result can be interpreted as:
0 cents= exact target frequency- Negative cents = flat
- Positive cents = sharp
For example, if the result displays:
A4 — +12 cents
the frequency is slightly higher than the exact A4 target.
If it displays:
A4 — -8 cents
the frequency is slightly lower.
The visual tuning meter makes this difference easier to interpret by placing the result between approximately -50 and +50 cents around the nearest note.
What Does Sharp, Flat, and In Tune Mean?
The converter classifies the direction of the frequency difference.
In tune means the entered value is effectively centered on the calculated target frequency.
Sharp means the measured frequency is higher than the target.
Flat means it is lower.
This does not mean a performance is musically good or bad. The display only describes the mathematical relationship between the entered frequency and the nearest note under the selected tuning reference.
If you are working with actual recorded or live sound, a frequency value can also vary because of vibrato, pitch drift, harmonics, noise, or the way the original pitch was measured.
A4 = 440 Hz and Alternative Reference Pitch
The converter defaults to:
A4 = 440 Hz
Changing this reference moves the frequency assigned to every note while keeping the same equal-tempered interval structure.
For example, using A4 = 442 Hz makes all corresponding note frequencies slightly higher than they would be under A4 = 440 Hz.
This can be useful when working with:
- orchestral tuning references
- historical or alternative pitch standards
- instruments tuned above or below 440 Hz
- recordings created with a different reference pitch
Changing A4 does not change the temperament itself. The calculator continues to use 12-tone equal temperament.
Common Hz to Note Examples
Using A4 = 440 Hz, several familiar note frequencies are:
| Frequency | Nearest Note |
|---|---|
| 110 Hz | A2 |
| 220 Hz | A3 |
| 261.626 Hz | C4 |
| 329.628 Hz | E4 |
| 440 Hz | A4 |
| 523.251 Hz | C5 |
| 659.255 Hz | E5 |
| 880 Hz | A5 |
These values illustrate the octave relationship clearly. Every time the frequency of the same note name doubles, the pitch moves up one octave.
If you need to work more broadly with frequencies rather than note names, the Frequency Calculator can complement this converter.
Convert a Musical Note Back to Hz
The tool also includes a Note → Hz mode.
Select:
- Note name
- Octave
- A4 reference
and the converter calculates the corresponding equal-tempered frequency.
For example:
A4 at A4 = 440 Hz → 440 Hz
A5 at A4 = 440 Hz → 880 Hz
This reverse mode is useful when you know the musical note but need a precise frequency for synthesis, testing, filtering, software development, oscillator settings, or other technical audio work.
MIDI Note Numbers
The converter also reports the MIDI note number associated with the nearest pitch.
Under standard MIDI numbering:
- C4 = MIDI 60
- A4 = MIDI 69
- C5 = MIDI 72
MIDI numbers provide a convenient numerical way to represent chromatic pitches and are frequently used in synthesizers, DAWs, MIDI controllers, plugins, and audio software.
A MIDI note number identifies pitch position, while the exact frequency depends on the tuning reference being used.
Understanding the Frequency Difference
In addition to cents, the converter displays the direct difference in Hertz between the entered frequency and the calculated target.
For example:
Input:
442 Hz
Target A4 under 440 Hz tuning:
440 Hz
Frequency difference:
+2 Hz
However, Hertz differences should not be interpreted in isolation because musical pitch perception is logarithmic.
A 2 Hz difference at a low frequency represents a larger musical interval than the same 2 Hz difference at a very high frequency. Cents are therefore usually more useful for comparing tuning differences across the musical range.
Why the Converter Shows Neighboring Notes
The previous and next note displays provide additional context around the result.
Instead of only seeing:
A4
you can also see the neighboring semitones and their frequencies.
This helps when a measured frequency is near the boundary between two musical notes.
The tool also calculates lower and upper classification boundaries around the nearest note. These boundaries represent the halfway points, in pitch distance, between the current note and its neighboring semitones.
Hz to Note Converter vs Pitch Detector
These tools solve different problems.
The Hz to Note Converter is best when you already know the numerical frequency.
The Pitch Detector is more appropriate when you want the browser to analyze sound and estimate its pitch automatically.
For example:
If an audio analyzer reports 329.4 Hz, use the Hz to Note Converter to interpret that number as a musical pitch.
If you are playing a note into your microphone and do not know its frequency yet, use a pitch-detection tool first.
Frequency, Pitch, and Audio Latency
Frequency describes how many cycles occur per second and is measured in Hertz.
Pitch is the musical perception associated with frequency, although real-world pitch perception can also be influenced by harmonics, timbre, and other acoustic factors.
Neither should be confused with audio latency, which describes a time delay in an audio system.
If you are investigating delayed sound rather than pitch, use the Audio Latency Test or read about how sample rate and latency interact in digital audio systems.
Accuracy and Limitations
The converter uses mathematical equal-tempered note relationships, so the numerical conversion itself is deterministic for a given frequency and A4 reference.
However, the usefulness of the result depends on the quality of the input frequency.
If a frequency came from a live pitch detector, microphone recording, spectrum analyzer, or other measurement system, that original measurement may contain uncertainty.
Real musical sounds also contain harmonics rather than one perfectly isolated sine-wave frequency.
The tool assumes:
- 12-tone equal temperament
- a user-selected A4 reference
- a valid positive input frequency
It does not automatically identify alternative temperaments, musical keys, chords, instruments, or tuning systems.
Privacy
All conversions happen locally in your browser.
The tool does not need microphone permission when you manually enter a frequency, and no audio file is required.
Recent conversions may be stored temporarily in session storage so you can compare values during the current browsing session.
Frequently Asked Questions
What musical note is 440 Hz?
With A4 set to 440 Hz, 440 Hz is exactly A4.
What note is 432 Hz?
If your reference remains A4 = 440 Hz, 432 Hz is slightly flat relative to A4. If you change the tuning reference itself to A4 = 432 Hz, then 432 Hz becomes the exact A4 reference note.
What frequency is middle C?
With A4 = 440 Hz and 12-tone equal temperament, C4 is approximately 261.626 Hz.
How do I convert Hz to a musical note?
The converter measures the logarithmic semitone distance between the entered frequency and the selected A4 reference, then chooses the nearest equal-tempered note.
How many cents are in one semitone?
One equal-tempered semitone contains 100 cents.
What does +20 cents mean?
It means the frequency is 20 cents higher, or sharper, than the exact target note.
What does -20 cents mean?
It means the frequency is 20 cents lower, or flatter, than the target.
Can I use A4 = 432 Hz?
Yes. Change the A4 reference to 432 Hz and the converter will recalculate all note frequencies relative to that reference.
Is a Hz to Note Converter the same as a tuner?
Not exactly. This converter works from a supplied frequency value. A live tuner or pitch detector must first analyze an audio signal to estimate that frequency.
Does changing A4 change the musical temperament?
No. Changing the reference pitch shifts the note frequencies, but this tool continues to use 12-tone equal temperament.