Note Frequency Calculator — note name ⇄ Hz, MIDI, cents

Real-world use cases

• Tune an instrument to a reference pitch by ear

  You left your clip-on tuner at home and need to get a guitar's A string close before a jam. Pick A2 (MIDI 45, 110 Hz at A4 = 440), hit Play, and match the open string to the sine tone. Then check the rest: low E is E2 (82.41 Hz), D is D3 (146.83 Hz). Because the preview is a pure sine, beating against your string is easy to hear — when the wobble slows to nothing, you're locked in.

• Match a 432 Hz recording in your DAW

  A collaborator sent stems tuned to A4 = 432, but your project is at the 440 default and everything clashes. Switch the reference to 432 here, look up the frequencies you need (middle C becomes 256.87 Hz instead of 261.63), and set your synth's master tune or pitch knob to the −31.8 cent offset the tool reports. Now your software instruments sit in the same tuning as the imported audio.

• Set an oscillator frequency on a hardware or software synth

  Building a drone patch and you want the sub oscillator sitting on a specific note rather than an arbitrary Hz value. Type the note (say C1), read 32.70 Hz, and dial that into the oscillator's frequency field. For analog gear without note-name entry this is the fastest way to land on a musical pitch instead of guessing.

• Write or debug a MIDI file by hand

  You're hand-editing a MIDI track and need the right note numbers. Flip to Frequency → Note, paste in a frequency you measured from a sample (e.g. 196 Hz), and the tool tells you it's G3, MIDI 55, two cents flat. Now you know exactly which note-on byte to write and how far the sample drifts from concert pitch.

• Teach equal temperament and the octave ratio in class

  Demonstrating to students why an octave is a 2:1 ratio: show A4 = 440, then A5 = 880, then A3 = 220 — each octave doubles or halves. Pull up C4 and C5 to show the same doubling holds for any note, and use the cents readout to explain why a 432 tuning is "the same music, shifted down a third of a semitone." The audible preview makes the ratio click in a way a number on the board can't.

Common pitfalls

• Confusing the octave numbering. This tool uses scientific pitch notation, where middle C is C4 and A4 = 440. Some DAWs and synths label middle C as C3 (Yamaha) or C5 (older Roland), which shifts every octave label by one. The MIDI number (middle C = 60) is unambiguous — when in doubt, match on MIDI, not on the octave digit.

• Reading cents as a frequency error in Hz. Cents are logarithmic, not linear. 10 cents at A4 (440 Hz) is about 2.5 Hz, but 10 cents at A2 (110 Hz) is only about 0.6 Hz. Don't assume "5 cents off" means the same Hz gap at the bottom and top of the keyboard.

• Expecting 432 Hz to be "more correct." A4 = 432 is a valid alternative tuning, not a more natural or scientifically superior one. It simply re-anchors equal temperament about 31.8 cents lower. If you're recording with others on standard gear, a 432 master tune will leave you a third of a semitone flat against everyone else.

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