Pitch Notation Converter - Scientific, Helmholtz and MIDI Numbers

Use the free tool below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.

Why pitch needs several notations

A single pitch, say the A above middle C, can be written as A4, a’, MIDI 69, or 440 Hz. Each notation belongs to a different world. Scientific pitch notation belongs to textbooks and acoustics. Helmholtz notation belongs to older scores and organ music. MIDI numbers belong to electronic instruments and software. Frequencies belong to physics and tuners. A musician who moves between these worlds needs to translate fluently.

The confusion usually starts with octaves. In scientific notation, middle C is C4, and the octave changes at C, so the B below middle C is B3. In Helmholtz notation, middle C is c’ with one tick mark, and the octave below it is written with a capital letter and no tick. MIDI numbers avoid the problem by counting every semitone from 0, so middle C is 60 and every octave is exactly 12 numbers.

Scientific pitch notation

Scientific notation writes the note name followed by an octave number: C4, F sharp 3, B flat 2. The number rises at each C, which means the octave from C4 to B4 contains the notes C, D, E, F, G, A and B in that octave. Middle C is C4 in the most common standard, used by most American textbooks and by MIDI software. Some European standards call middle C C3, which is a known source of confusion, so always check which standard a source uses.

Scientific notation is the clearest for talking about exact pitches in writing, because it removes all doubt about which octave you mean. When a singer asks what octave a note is in, C4 is a precise answer in a way that just C is not.

Helmholtz notation

Helmholtz notation, invented by the physicist Hermann von Helmholtz, uses letter case and marks instead of numbers. The great octave, C2 to B2 in scientific notation, is written with capitals and one comma: C, to B,. The small octave, C3 to B3, is written with plain capitals: C to B. The one line octave, C4 to B4, uses lowercase letters with one tick: c’ to b’. Each higher octave adds a tick, and each lower octave adds a comma.

Helmholtz notation looks old fashioned, but it is compact and still appears in organ music, acoustics books and some European scores. It is also the notation that makes the structure of octaves visible: the tick marks literally count how far you are from the middle of the range.

MIDI numbers and frequencies

MIDI numbers count semitones from C minus 1, which is MIDI 0. Middle C is 60, the A above it is 69, and concert pitch, the A orchestras tune to, is 440 Hz. The formula linking them is simple: frequency equals 440 times 2 to the power of the semitone distance from A4 divided by 12. That formula is why every semitone is the same ratio, about 1.05946, and why octaves double the frequency.

Frequencies matter for tuners and instrument makers. A tuner does not care about note names: it measures a frequency and tells you how far you are from the nearest equal tempered note, in cents. The converter shows that deviation too, so a frequency of 445 Hz reads as A4, about 20 cents sharp.

How to use the converter

Enter a pitch in any of the three forms: a scientific note like C4, a MIDI number like 60, or a frequency like 440. The converter returns all the other forms at once. Try middle C in each form and watch the same pitch appear as C4, c’, 60 and 261.63 Hz. Then try a frequency that is slightly off, like 445, and see how the converter reports the nearest note plus the cents deviation.

Use the converter when reading a score that uses Helmholtz, when programming a MIDI device, when setting up a synthesiser, or when a tuner gives you a frequency and you want to know which note it really is.

Common mistakes

The most common mistake is the octave boundary: the B below middle C is B3, not B4, because octaves change at C. The second is mixing Helmholtz ticks and commas: ticks go up, commas go down, and the small octave has neither. The third is assuming every source calls middle C C4: some call it C3, so when a MIDI device and a textbook disagree by one octave, check the standard before assuming an error.

Convert a few pitches now, and the four notations will start to feel like four ways of saying the same thing, which is exactly what they are.

Pitch Notation Converter – Scientific, Helmholtz and MIDI Numbers