Frequency to Note Converter
Convert any frequency in Hz to the nearest musical note with cents offset, or find the exact frequency of any note. Supports A4 = 432, 440, or 442 Hz — free, browser-based, no download.
→ Frequency to Note
← Note to Frequency
How to Use the Converter
- Hz → Note: Enter a frequency in Hz (e.g., 440) to see the nearest note, octave, and cents offset.
- Note → Hz: Click a note name and octave to see its exact frequency.
- Change the A4 reference (432 / 440 / 442 Hz) if your instrument uses non-standard tuning.
- Toggle flats (♭) if you prefer Db over C#, Bb over A#, etc.
- Use the quick buttons for common reference frequencies and notes.
The Conversion Formula
The relationship between frequency and musical notes is based on the equal-tempered scale, where each octave is divided into 12 equal semitones. Given a reference frequency for A4 (standard: 440 Hz), any note's frequency can be calculated:
f = A4 × 2(n − 69) / 12
where n is the MIDI note number (A4 = 69) and A4 = 440 Hz
To go the other direction — frequency to note — invert the formula:
n = 69 + 12 × log2(f / A4)
The integer part of n gives the nearest MIDI note (which maps to a note name and octave), and the fractional part multiplied by 100 gives the cents offset — how far the frequency is from the exact note.
Note Frequency Reference Table
Standard equal-tempered frequencies for common musical notes (A4 = 440 Hz). Use this as a quick lookup for instrument tuning and audio calibration.
| Note | Frequency | MIDI | Common Use |
|---|---|---|---|
| C0 | 16.35 Hz | 0 | Lowest audible piano-style note |
| A0 | 27.50 Hz | 21 | Lowest key on a standard 88-key piano |
| E1 | 41.20 Hz | 28 | Lowest note on a 4-string bass (B0 on 5-string) |
| E2 | 82.41 Hz | 40 | Low E string — guitar (standard tuning) |
| A2 | 110.00 Hz | 45 | A string — guitar |
| C3 | 130.81 Hz | 48 | Low C — cello C-string |
| G3 | 196.00 Hz | 55 | G string — guitar / violin G-string |
| C4 | 261.63 Hz | 60 | Middle C — piano center |
| A4 | 440.00 Hz | 69 | Concert pitch reference (ISO 16) |
| C5 | 523.25 Hz | 72 | C one octave above middle C |
| A5 | 880.00 Hz | 81 | A one octave above A4 |
| C8 | 4186.01 Hz | 108 | Highest key on a standard piano |
Frequently Asked Questions
Use the formula MIDI = 69 + 12 × log2(frequency / 440). The integer part maps to a note name and octave; the fractional part gives the cents offset. For example, 440 Hz → A4 (0 cents), 261.63 Hz → C4 (0 cents).
A4 = 440 Hz in standard concert pitch (ISO 16:1975). Some orchestras use 442 Hz for a brighter sound. This converter supports 432, 440, 442 Hz, or any custom A4 value between 400–460 Hz.
A cent is 1/100 of a semitone. There are 100 cents between adjacent notes (e.g., C4 and C#4). The cents offset shows how far a frequency is from the nearest standard note. +5 cents = 5 cents sharp; −3 cents = 3 cents flat. Most people can't hear differences smaller than 5–10 cents.
frequency = A4 × 2^((MIDI − 69) / 12). With A4 = 440 Hz, C5 (MIDI 72) = 440 × 2^(3/12) ≈ 523.25 Hz. This converter calculates it instantly — just pick a note and octave.
Most real-world frequencies don't land exactly on a standard equal-tempered note. 445 Hz is about 19 cents sharp of A4 (440 Hz). The cents offset tells you the tuning deviation — useful for instrument tuning and acoustic analysis.
440 Hz is the international standard (ISO 16) since 1955. 442 Hz is used by some European orchestras for brightness. 432 Hz is a popular alternative with no proven audio advantage but some prefer its warmer tone. All three are supported here.