435 Hz: the French diapason of 1859

In 1859 France fixed A4 at 435 Hz by law to stop orchestral pitch from creeping ever higher. The “diapason normal” was widely adopted across Europe and stood until the 440 standard replaced it in the 20th century.

Which note 435 Hz is at other reference pitches

“In tune” depends on what A4 is tuned to, so the same frequency is a slightly different distance from the nearest note in each tuning.

An octave of notes at A4 = 435 Hz

Middle C to the C above, tuned to this reference, beside the same notes at the 440 standard.

Octaves of 435 Hz

Doubling a frequency raises it an octave and halving lowers it one, so these all have the same note name and the same offset from it.

• 54.38 Hz · A1
• 108.75 Hz · A2
• 217.50 Hz · A3
• 870.00 Hz · A5
• 1740.0 Hz · A6
• 3480.0 Hz · A7

Harmonics of 435 Hz

A real instrument playing 435 Hz also sounds whole-number multiples of it. The first eight, and the notes they fall nearest:

Period and wavelength

One cycle of 435 Hz lasts 2.299 milliseconds; in air at 20 °C, where sound travels at about 343 metres a second, one wavelength is 78.9 centimetres.

Convert another frequency

Or hold 435 Hz as a steady tone, sweep from it, or beat it against a second tone in the tone generator. The note frequency chart lists every note from C0 to B8.

Frequently asked questions

Related frequencies

• 440 Hz — the standard tuning pitch
• 432 Hz — an alternative tuning pitch
• 430 Hz — a period tuning pitch