A=440 Hz Concert Pitch — Note Frequencies

About A=440 Hz

A=440 Hz is defined by ISO 16:1975 as the international concert pitch standard. This standard was first adopted at the 1939 London international conference, bringing together representatives from national standards bodies across Europe and North America. Before 1939, concert pitch varied widely among orchestras — ranging from approximately 415 Hz to 452 Hz — making ensemble coordination and instrument manufacturing inconsistent.

Under A=440 Hz, all 12-tone equal temperament frequencies are derived using the formula f = 440 × 2^((MIDI − 69) / 12). Every note across all octaves is defined relative to this single reference. This mathematical anchoring makes A=440 the foundation of modern instrument manufacturing, electronic tuner calibration, and pitch notation.

Despite its official status, some orchestras tune slightly above 440 Hz for a brighter ensemble sound — commonly 441–445 Hz. The ISO standard remains the universal reference point for tuners, synthesizers, and fixed-pitch instruments such as piano and organ.

Chromatic Note Frequencies at A=440 Hz

All 12 chromatic notes in equal temperament, calculated at A=440 Hz reference pitch across octaves 3, 4, and 5. Hz values are rounded to 3 decimal places.

Frequencies computed from f = 440 × 2^{(MIDI − 69) / 12} where A4 MIDI = 69. The highlighted row is A, the concert pitch reference note at this standard.

Other Concert Pitch Standards

• A=432 Hz — Alternative Tuning
• A=442 Hz — European Orchestral
• A=443 Hz — High European / Asian Orchestral
• A=415 Hz — Baroque Pitch (HIP)

Related Reference Pages

• A4 note page — full temperament frequency data
• Note frequency hub — all 153 notes
• Concert pitch hub — compare all 5 standards