MIDI Note Number Calculator

Frequently Asked Questions

How do MIDI note numbers map to pitch?

MIDI note 69 is A4 = 440 Hz. Each step is one semitone, so frequency = 440 × 2^((note − 69) ÷ 12). Middle C is MIDI 60 (in the common C3-as-60 convention may differ by octave naming).

What is the MIDI note range?

MIDI notes run 0–127. Note 0 is C−1 (~8.18 Hz), note 127 is G9 (~12,544 Hz). Most music lives between MIDI 21 (A0, piano lowest) and 108 (C8, piano highest).

Why do octave numbers sometimes disagree?

There are two conventions: middle C as C3 (Yamaha) or C4 (Roland/scientific). The MIDI number (60 = middle C) is unambiguous; only the displayed octave label changes between standards.

How do I convert a note name back to MIDI?

Number = 12 × (octave + 1) + pitch class, with C = 0, C# = 1 … B = 11 (C4 convention). A4 = 12 × 5 + 9 = 69, matching the 440 Hz reference.

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How This Calculator Works

The MIDI protocol identifies every pitch with a single integer from 0 to 127. This calculator converts freely between three representations: the MIDI note number, the note name plus octave (like C4 or A#5), and the frequency in hertz. It works in both directions - type a MIDI number to get its name and pitch, or type a note name and octave to get its MIDI number and frequency. Frequencies use twelve-tone equal temperament with an adjustable A4 reference (default 440 Hz), so the tool doubles as a tuning reference for synths, samplers, and notation software. Anyone programming a hardware synth, mapping a multisampled instrument, scripting an arpeggiator, or debugging a MIDI controller eventually needs this three-way conversion, and doing it by hand invites octave-numbering errors. Keeping note number, name and frequency visible together also makes it obvious when two devices disagree about where middle C sits - the most common source of "everything is an octave off" bugs in a studio signal chain.

Formula / Method

By the MIDI standard, note 69 is A4. The frequency of any MIDI note m is f = ref × 2^{((m − 69) ÷ 12)}, because each MIDI step is one equal-tempered semitone (a ratio of 2^1÷12). To name a number, the pitch class is m mod 12 (0 = C, 11 = B) and the octave is ⌊m ÷ 12⌋ − 1, which makes middle C = MIDI 60 = C4. Going the other way, m = (octave + 1) × 12 + pitch-class index. The waveform period is 1000 ÷ f milliseconds.

Worked Example

MIDI 60: pitch class 60 mod 12 = 0 (C), octave ⌊60÷12⌋ − 1 = 4, so the name is C4 (middle C). Its frequency is 440 × 2^{((60 − 69)÷12)} = 440 × 2^−0.75 ≈ 261.63 Hz. Going the other way, A4: pitch-class index of A is 9, octave 4, so MIDI = (4 + 1) × 12 + 9 = 69, frequency 440 × 2⁰ = 440 Hz exactly. Switch the reference to 432 Hz and MIDI 60 instead yields about 256.87 Hz - the same note number, a globally shifted pitch.

Common Mistakes

Octave numbering: this tool uses MIDI 60 = C4 (middle C); some DAWs label the same note C3 or C5.

Treating sharps and flats as different MIDI numbers - C# and Db are the same note (enharmonic).

Going outside 0–127; standard MIDI cannot address notes beyond that range.

Assuming velocity is pitch - the note number is pitch, velocity is a separate 0–127 loudness value.

Forgetting pitch-bend and microtuning add a fractional offset on top of the integer note.

Tips & FAQ

Why is middle C ambiguous? MIDI fixes A4 = 69 but never standardised the octave label, so middle C is variously written C3, C4 or C5; this tool uses the common scientific C4 = 60. If a sample plays back an octave too high or low, the first thing to check is whether the two pieces of software use different octave conventions for the same note number. What is MIDI 0 and 127? Note 0 is C−1 (about 8.18 Hz, sub-audible) and 127 is G9 (about 12,544 Hz) - the protocol's full addressable range, which comfortably exceeds the span of a grand piano (MIDI 21 to 108). Can I retune everything? Yes - change the A4 reference and every frequency scales together while note numbers stay fixed, exactly how a global master-tune control behaves; this is how you match a synth to an instrument tuned to 442 Hz without re-keying a part. Is this useful for sampler mapping? Very - knowing a sample's root note number and frequency lets you set pitch-tracking and key zones correctly across the keyboard, so a single recording can be transposed cleanly across a wide range without the chipmunk or muddy artefacts that come from stretching it too far.

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