Musical Note Frequency Calculator

Find any note's frequency in equal temperament at your chosen tuning.

What it does

Equal temperament divides the octave into twelve equal steps, so every semitone multiplies frequency by the twelfth root of two. That single rule generates the frequency of every note once one reference is set.

The reference is A4, and ISO 16:1975 fixed it at 440 Hz for instrument makers and broadcasters. Orchestras sometimes drift higher for brightness, with 442 and 443 common in Europe, and historically informed groups tune to 415 for Baroque pitch.

The tool above maps the note and octave to a MIDI number, then applies the equal temperament formula. The defaults return middle C: MIDI note 60, 261.63 Hz when A4 sits at 440.

MIDI numbering makes the arithmetic tidy because A4 is note 69. Each step of 12 in the MIDI number doubles the frequency, so C5 lands at 523.25 Hz, exactly twice middle C, and A3 lands at 220 Hz, half of A4.

The math assumes equal temperament, where every key is slightly mistuned from pure ratios to allow free modulation. String quartets and a cappella groups shade toward just intonation by ear, so the printed frequency is the target, not the last word.

How to use

1. Pick the note name, sharps included.
2. Enter the octave using scientific notation.
3. Adjust concert pitch if your ensemble uses one.
4. Read the frequency in hertz.
5. Check the MIDI number for DAW work.
6. Compare two octaves to see the exact doubling.

Formula

f

Frequency in hertz for the selected note.

n

MIDI note number, 69 for A4 (440 Hz).

A4

Concert pitch reference in hertz, 440 by ISO 16.

octave

Scientific octave number, with C4 as middle C.

The exponent divides the semitone distance from A4 by 12, so 12 semitones up multiplies by exactly 2. Sharps are treated as the twelve equal steps; enharmonic names like A# and Bb share a frequency. The tuning input lets you match Vienna at 443 or a period ensemble at 415.1 without changing anything else about the math.

Worked example

Reference table

Limits

• Equal temperament only; just intonation differs by a few cents.
• Fixed A4 reference; no stretch tuning as pianos use.
• Octave conventions matter: C4 here is middle C, MIDI 60.
• Instrument inharmonicity and playing technique move real pitches.

Common mistakes

• Counting middle C as C3 instead of C4 in scientific notation.
• Assuming 440 Hz everywhere; European orchestras often sit at 442 or 443.
• Confusing hertz differences with cents, which are logarithmic.
• Expecting a piano's top octave to match the formula exactly, stretch tuning aside.
• Reading A# and Bb as different pitches; equal temperament makes them one.

Try it yourself

Quick checks. Answers sit tucked under each question.

Questions

Sources

• HyperPhysics: equal temperament and note frequencies
• ISO 16:1975, standard tuning frequency (A = 440 Hz)

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