Note to Frequency Calculator
Convert musical notes to their frequency in Hz, or enter a frequency to find the nearest musical note.
Based on A4 = 440 Hz standard tuning.
Sound frequency and pitch are directly related: frequency (measured in Hz — cycles per second) determines what pitch we hear. The Western musical scale is built on a logarithmic system where each octave doubles the frequency, and each of the 12 semitones within an octave divides this doubling equally.
Frequency of any note formula: f = f₀ × 2^(n/12)
Where:
- f = frequency of the target note (Hz)
- f₀ = reference frequency (standard tuning: A4 = 440 Hz)
- n = number of semitones above (+) or below (−) the reference note
- 2^(1/12) = the twelfth root of 2 ≈ 1.05946 — the frequency ratio between adjacent semitones
Frequency ratios of musical intervals:
- Unison: 1:1
- Minor 2nd (1 semitone): 1.0595:1
- Major 2nd: 1.1225:1
- Minor 3rd: 1.1892:1
- Major 3rd: 1.2599:1
- Perfect 4th: 1.3348:1
- Perfect 5th: 1.4983:1
- Octave: 2:1 exactly
Standard note frequencies (A440 tuning):
- A3: 220 Hz; A4: 440 Hz; A5: 880 Hz
- Middle C (C4): 261.63 Hz
- B4: 493.88 Hz; C5: 523.25 Hz
Wavelength formula: λ = v ÷ f Where v = speed of sound ≈ 343 m/s at 20°C, f = frequency in Hz.
Worked example: Find the frequency of C5 (middle C is C4 = 261.63 Hz, C5 is one octave above):
- C5 = C4 × 2^(12/12) = 261.63 × 2 = 523.25 Hz
Find the frequency of D4 (D is 2 semitones above A4? No — D4 is a specific note): n from A4 to D4: A4 → A#4 → B4 → C5… wait, going DOWN: A4 → G#4 → G4 → F#4 → F4 → E4 → D#4 → D4 = −7 semitones f(D4) = 440 × 2^(−7/12) = 440 × 0.6674 = 293.66 Hz
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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