Look up the frequency of any note in hertz, or go the other way: type in Hz and find the nearest note and how many cents off it is. Below you'll find a full note frequency chart from C0 to B8, with MIDI note numbers and periods.
Everything is calculated in your browser from the reference pitch you choose (A4 = 440, 442, 432 Hz…), and the chart updates instantly.
How to use it
- In Note → frequency, choose a note and octave to see its Hz, MIDI number, wavelength and period.
- In Frequency → note, type in the Hz. Positive cents: above the note; negative: below it.
- Tap Listen to hear the note or the frequency.
- In the chart, search by name (
C4,C#3) or by Hz, and use Copy chart to paste it into a spreadsheet.
The formula and equal temperament
In equal temperament, the tuning of pianos and guitars, the octave is split into 12 equal semitones (half steps): each semitone multiplies the frequency by 21/12 ≈ 1.0595, and the octave doubles it. Hence f = 440 × 2^((n − 69) / 12), where n is the MIDI note number (A4 = 69, C4 = 60).
A cent is one hundredth of a semitone, so an octave has 1200. The tempered fifth is 2 cents narrower than a pure one, and the major third almost 14 cents wider.
Why A4 is 440 Hz
Until the 20th century, each country tuned to its own A; France used 435 Hz. In 1939 an international conference in London set 440 Hz, later standardized as ISO 16. Many orchestras tune to 442 or 443 Hz. 432 Hz sits about 32 cents lower and has no proven special effect.
Middle C: C4 or C3?
This chart uses scientific pitch notation: middle C is C4 (MIDI note 60, 261.63 Hz) and the tuning-fork A is A4. Many DAWs and keyboards (Yamaha, Ableton, Cubase, Logic) label MIDI note 60 as C3, so their note names read one octave lower. The frequency is the same; when in doubt, go by the MIDI number.
Tips
- To tune by ear, let the note ring in the tone generator and play the string along with it: when the beating disappears, you're in tune.
- Bass guitar: E1 41.20 Hz, A1 55.00, D2 73.42 and G2 98.00; the low B0 of a 5-string bass is 30.87 Hz. Check them with the bass tuner.
- Ukulele in standard G C E A tuning: G4 392.00, C4 261.63, E4 329.63 and A4 440.00 Hz.
- Mains power is 60 Hz in North America (between A♯1 and B1) and 50 Hz in the UK, Europe, India and Australia (just above G1): if a recording hums, cut there and at the first harmonics.
- For an Arduino buzzer,
tone()takes whole numbers: round the chart value, so A4 is 440 and C5 is 523.
Frequently asked questions
What is the frequency of middle C?
261.63 Hz with A4 = 440 Hz (262.82 Hz with A4 = 442). It is C4 in scientific pitch notation and MIDI note 60; some programs call it C3.
Why is A4 tuned to 440 Hz?
Because of an international agreement (1939, later ISO 16) that lets instruments everywhere play together. Each octave doubles or halves the frequency: A2 is 110 Hz, A3 220, A5 880.
What are the guitar string frequencies?
From the 6th string to the 1st: E2 82.41 Hz, A2 110.00, D3 146.83, G3 196.00, B3 246.94 and E4 329.63 (check them with the guitar tuner).
How do I convert a frequency to a note?
Calculate n = 69 + 12 × log₂(f / 440): the nearest whole number is the MIDI note, and the remainder times 100 is the cents. 450 Hz gives 69.39: A4 +39 cents.
What MIDI note number is middle C?
60. A4 is 69, and each semitone adds 1: C♯4 is 61 and C5 is 72. The MIDI number is the safest reference, because it doesn't depend on how a program numbers its octaves.
What are the note frequencies with A = 432 Hz?
Every note is about 32 cents lower than at 440: middle C becomes 256.87 Hz. Choose 432 in the Reference A selector and the whole chart is recalculated. There is no evidence for the benefits often claimed for it.
How many cents are in a semitone?
100 in equal temperament; a whole step has 200 and an octave 1200.