Musical Note Frequency Calculator
Find the exact frequency of any musical note in Hz.
Calculate frequencies for all 88 piano keys, octaves, and equal temperament tuning.
Every musical note corresponds to a precise sound wave frequency measured in Hertz (Hz). In modern equal temperament tuning (12-tone ET), the octave is divided into 12 equally-spaced semitones, and each semitone has a fixed ratio to the next.
The formula: f(n) = 440 × 2^(n/12)
Where:
- f = frequency in Hz
- 440 = the reference pitch (A4 = 440 Hz, the international standard since 1939)
- n = number of semitones above or below A4 (positive = above, negative = below)
Key reference frequencies:
- A4 = 440 Hz (concert pitch / standard tuning reference)
- Middle C (C4) = 261.63 Hz
- A3 = 220 Hz (one octave below A4)
- A5 = 880 Hz (one octave above A4)
- C8 (highest piano key) ≈ 4,186 Hz
- A0 (lowest piano key) = 27.5 Hz
Octave relationship: Doubling the frequency raises the pitch by exactly one octave. A4 is 440 Hz, A5 is 880 Hz, A3 is 220 Hz.
Semitone ratio: Each semitone step multiplies the frequency by the 12th root of 2 ≈ 1.05946. Going up a semitone from A4 (440 Hz) gives A#4/Bb4 ≈ 466.16 Hz.
Concert pitch variations: Different orchestras sometimes tune to slightly different A4 references:
- A = 440 Hz: International standard (ISO 16)
- A = 442–444 Hz: Many European orchestras (brighter sound)
- A = 432 Hz: Alternative tuning promoted by some musicians
- A = 415 Hz: Historically used in Baroque music
Chord frequencies (based on A4 = 440 Hz): A C major chord (C–E–G): C4 = 261.63 Hz, E4 = 329.63 Hz, G4 = 392.00 Hz These notes have frequency ratios close to 4:5:6 (the just intonation ideal).