Equal-tempered pitch converter
Frequency Finder
Convert a musical note to Hertz or find the nearest note for any positive frequency.
Result
- Exact frequency
- —
- Nearest note
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- Enharmonic name
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- Ideal note frequency
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- Pitch difference
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- Frequency difference
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- Wavelength in air
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- Oscillation period
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- Previous semitone
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- Next semitone
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Recent conversions
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Frequency Finder
The Frequency Finder converts musical notes into exact frequencies and converts entered frequencies into the nearest equal-tempered note.
It supports both directions:
- Note to frequency: choose a note, accidental, and octave to calculate its frequency in Hertz.
- Frequency to note: enter a frequency to find the nearest note, octave, tuning difference, and related wave measurements.
The calculator uses twelve-tone equal temperament and lets you adjust the A4 reference pitch from 300 to 500 Hz. No microphone is used, and all calculations run in your browser.
How to Use the Frequency Finder
- Choose Note to frequency or Frequency to note.
- Enter the required note or frequency.
- Set the A4 reference pitch. The default is 440 Hz.
- Choose between 0 and 6 decimal places.
- Select Find frequency or Find note.
- Review the complete result, including cents, wavelength, period, and adjacent semitones.
Note to Frequency Mode
For note-to-Hz conversion, select:
- A note letter from C through B
- Natural, sharp, or flat
- An octave from −1 through 9
- An A4 reference between 300 and 500 Hz
- The desired decimal precision
The tool prevents unsupported spellings such as B sharp, E sharp, C flat, and F flat by returning those selections to natural notes.
Frequency to Note Mode
Enter any positive frequency from 0.01 Hz to 100,000 Hz.
The tool finds the nearest equal-tempered note and displays:
- The nearest note and octave
- An enharmonic name when one exists
- The ideal frequency of that note
- The difference in cents
- The difference in Hertz
This mode analyzes a typed number. It does not listen to live audio or detect pitch from a microphone.
How Note-to-Frequency Conversion Works
Musical notes in twelve-tone equal temperament are separated by equal frequency ratios. An octave contains 12 semitones, and moving up one octave doubles the frequency.
The plugin maps the selected note and octave to a MIDI-style note number. A4 corresponds to note number 69.
The frequency is then calculated as:
Frequency = A4 reference × 2^((note number − 69) ÷ 12)
At the default A4 reference of 440 Hz:
| Note | Frequency |
|---|---|
| A3 | 220 Hz |
| A4 | 440 Hz |
| A5 | 880 Hz |
| C4 | Approximately 261.63 Hz |
Changing the A4 reference changes every note frequency, not only the note A. For example, choosing A4 = 432 Hz recalculates the entire equal-tempered tuning system around that reference.
How Frequency-to-Note Conversion Works
For an entered frequency, the calculator first determines its exact position relative to A4:
Note position = 69 + 12 × log₂(frequency ÷ A4 reference)
That position is rounded to the nearest whole semitone to identify the nearest musical note.
The calculator then recomputes the ideal frequency for that note. The difference between the entered frequency and the ideal note is displayed in both cents and Hertz.
This provides more context than returning only a note name. Two frequencies may map to the same nearest note while being differently sharp or flat.
How to Read Every Result
| Result | Meaning |
|---|---|
| Exact frequency | The calculated note frequency or the frequency you entered |
| Nearest note | The closest equal-tempered note and octave |
| Enharmonic name | An alternate flat name for the same pitch, when available |
| Ideal note frequency | The exact frequency of the nearest note at the selected A4 reference |
| Pitch difference | How sharp or flat the frequency is, measured in cents |
| Frequency difference | The signed difference between the entered and ideal frequencies |
| Wavelength in air | The calculated wavelength using 343 m/s |
| Oscillation period | The duration of one frequency cycle |
| Previous semitone | The note and frequency one semitone lower |
| Next semitone | The note and frequency one semitone higher |
Exact Frequency vs. Ideal Frequency
In note-to-frequency mode, the exact and ideal frequencies are the same because the tool generates the frequency directly from a defined equal-tempered note.
In frequency-to-note mode, they may differ:
- Exact frequency is the number entered.
- Ideal frequency is the calculated center frequency of the nearest note.
The difference shows how closely the input matches that note.
Understanding Cents
A cent is a proportional unit of musical pitch. There are 100 cents in one equal-tempered semitone.
The tool reports:
- A positive value when the frequency is sharp
- A negative value when it is flat
- Zero cents when it matches the ideal note at the selected precision
Cents are often more useful than raw Hertz for comparing tuning differences. A 1 Hz change represents a different musical interval at low and high frequencies, while cents measure the relative pitch distance.
Understanding Hertz Difference
The Hertz difference is calculated as:
Entered frequency − ideal note frequency
A positive result is above the ideal frequency. A negative result is below it.
This is useful when you need the actual numerical offset, while cents are better for understanding the musical size of that offset.
Enharmonic Note Names
In equal temperament, some sharp and flat names represent the same frequency.
Examples include:
- C♯ and D♭
- D♯ and E♭
- F♯ and G♭
- G♯ and A♭
- A♯ and B♭
The calculator displays the sharp spelling as the nearest note and shows the flat spelling as the enharmonic name when applicable. Natural notes display no alternate name.
A4 Reference Pitch
The default reference is A4 = 440 Hz, but the tool accepts any value from 300 to 500 Hz.
Changing the reference pitch affects:
- The selected note’s frequency
- The nearest note calculation
- The ideal frequency
- Cents and Hertz deviation
- Adjacent semitone frequencies
For meaningful comparisons, use the same A4 reference each time. A frequency judged against 440 Hz tuning may produce a different cents result when judged against 432 Hz tuning.
Wavelength and Oscillation Period
The tool calculates wavelength using a fixed speed of sound of 343 metres per second:
Wavelength = 343 ÷ frequency
Longer wavelengths correspond to lower frequencies. Shorter wavelengths correspond to higher frequencies.
The oscillation period is:
Period = 1 ÷ frequency
It represents the duration of one cycle. The tool displays longer periods in milliseconds and shorter periods in microseconds.
These values describe the physical wave. They do not measure musical quality, timbre, loudness, or how pleasant a sound is.
Common Frequency Conversion Mistakes
Treating semitones as equal Hertz steps:
Semitone spacing is based on a constant ratio, not a constant number of Hertz. The gap between adjacent notes becomes larger in Hertz as pitch rises.
Ignoring the octave number:
C3, C4, and C5 share a note letter but have different frequencies. Each octave increase doubles the frequency.
Assuming A4 affects only A notes:
A4 is the reference point for the full tuning system. Changing it recalculates every note.
Treating cents and Hertz as interchangeable:
Hertz measures absolute frequency difference. Cents measure proportional musical distance.
Expecting microphone detection:
This frequency finder converts entered values. It does not analyze recorded or live audio.
Input Limits and Browser History
The calculator supports:
| Setting | Allowed range |
|---|---|
| Frequency | 0.01–100,000 Hz |
| A4 reference | 300–500 Hz |
| Octave | −1 to 9 |
| Decimal precision | 0–6 places |
Copy Result copies a summary containing the conversion, nearest note, cents difference, and selected A4 reference.
Reset restores the original fields and hides the current result.
The calculator stores up to eight recent conversions in browser sessionStorage. Clear History removes those session results. The conversions are not stored as permanent account data by the plugin.
FAQ about Frequency Finder
How do I convert a musical note to frequency?
Choose Note to frequency, select the note, accidental, and octave, then set the A4 reference pitch. The calculator uses twelve-tone equal temperament to return the exact note frequency in Hertz.
How do I convert Hz to a musical note?
Choose Frequency to note and enter a value from 0.01 to 100,000 Hz. The Hz to note converter finds the nearest equal-tempered note and shows how sharp or flat the input is.
What note is 440 Hz?
At the default reference of A4 = 440 Hz, 440 Hz is A4. Changing the concert-pitch reference can change how another frequency is interpreted relative to the tuning system.
What frequency is Middle C?
Middle C is C4 in the octave system used by this calculator. At A4 = 440 Hz, its frequency is approximately 261.63 Hz.
What do positive and negative cents mean?
Positive cents mean the frequency is sharp relative to the nearest ideal note. Negative cents mean it is flat, while zero cents indicates alignment at the selected display precision.
Why do two note names sometimes have the same frequency?
Sharp and flat names such as C♯ and D♭ are enharmonic equivalents in twelve-tone equal temperament. The Frequency Finder displays the alternate flat spelling when one exists.
Can I use A4 = 432 Hz?
Yes. Enter 432 in the A4 reference field, and the calculator will recalculate all note frequencies and tuning differences around that reference.
Does the Frequency Finder detect live audio?
No. It converts selected notes and typed frequency values rather than listening through a microphone. This makes it a numerical note frequency calculator, not a live pitch detector.