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Every note has a number, and that number is its frequency
When you play an A above middle C on a piano, the string or speaker moves back and forth 440 times every second. That number, 440 hertz, is the frequency of the note. Every other note has its own frequency too, and the full set of them forms a chart that musicians, instrument makers, sound engineers and students use every day. This page gives you that whole chart, from the lowest C on a piano-style range up to the highest C, with the exact frequency of each note.
The chart is built on one simple rule. In the modern equal temperament system, each semitone step multiplies the frequency by the twelfth root of two, about 1.05946. That is why an octave, which is twelve semitone steps, exactly doubles the frequency. A4 at 440 hertz becomes A5 at 880 hertz and A3 at 220 hertz. Once you know one note, the whole chart follows from that rule, and the tool above computes all 97 notes from C0 to C8 for you.
How to use the frequency chart
Start by choosing your reference pitch. Modern standard is A440, and it is the default. If you play with a baroque ensemble, choose A415. If your orchestra tunes a little sharp, A442 is common. You can also type any custom reference between 100 and 1000 hertz, and the whole chart rebuilds at once. Then choose an octave if you only want one row of notes, or leave it on all octaves to see the full picture.
Each row shows the note name, its MIDI number and its frequency in hertz. MIDI numbers are the numbers that keyboards and music software use behind the scenes: middle C, C4, is MIDI 60, and every semitone up adds one. If you work in a digital audio workstation, the MIDI column lets you match a note in your piano roll to its real-world frequency in seconds.
The download button saves the chart as a CSV file, which opens in any spreadsheet. That is handy if you are building a lesson sheet, tuning a homemade instrument, or checking frequencies offline. The file contains exactly the rows shown on screen, so filter to one octave first if you want a short file.
Why frequencies matter in practice
Tuning is the most obvious use. A guitar tuner compares the frequency it hears with the target frequency of the open string, and a tuner app is really just a frequency chart with a microphone attached. If you know that the low E string of a guitar should be 82.41 hertz, you can judge any tuner reading yourself instead of trusting a green light blindly.
Sound design is another use. A low bass note at 55 hertz feels very different from the same note played an octave up at 110 hertz, even though the note name is the same letter. Sub-bass speakers, room acoustics and equaliser settings all depend on these numbers: a room that booms at 60 hertz will colour every note near B1, and knowing the chart helps you find the problem instead of guessing.
Singers benefit too. A soprano who knows her top note is around 1046 hertz, which is C6, can compare parts and choose repertoire that fits her voice. A choir director can check whether a written part sits too high or too low for a section by reading the frequencies, not just the note names.
Common mistakes with frequency charts
The most common mistake is mixing up octaves. Middle C is C4 in the scientific system used here, but some software calls it C3 or C5. The frequency is the same, about 261.63 hertz at A440, whatever label your software uses, so always check the hertz value when two sources disagree. Another mistake is assuming A440 is a law of nature. It is a convention, agreed in the twentieth century, and older music used lower references. That is exactly why this tool lets you change the reference.
Finally, remember that real instruments are not perfect sine waves. A piano note at 440 hertz also produces overtones at roughly 880, 1320 and 1760 hertz, and those overtones are what make a piano sound like a piano rather than a pure electronic beep. The chart gives the fundamental frequency, the main pitch you hear, and that is the right number for tuning, transposition and study.
Try it yourself
Pick a note you play often, find its frequency at A440, then switch the reference to A432 and watch every number drop slightly. That small shift is the whole debate about concert pitch in one table. Then download the chart, keep it beside your instrument, and you will never need to guess a frequency again.