Written by Vincent Sullivan | Last updated: June 2026
About the Tool
What does the Online Pitch Detector measure? The tool measures the fundamental frequency (F0) of a sound captured through your microphone in real time and displays three values: the frequency in Hz, the nearest musical note in equal temperament (A4 = 440 Hz), and the cents deviation — how many cents sharp or flat the detected frequency is from that note’s exact equal temperament pitch. For the complete technical pipeline, see the How It Works page.
Why does this tool show cents deviation when most pitch detectors just show a note name? A note name tells you which note you are closest to. Cents deviation tells you how close — and in what direction. For intonation work, the note name alone is insufficient: A4 at 437 Hz and A4 at 443 Hz are both “A4” by note name, but they are −11.8 cents and +11.8 cents respectively — a difference that is clearly audible to trained musicians and critical for professional tuning. Cents deviation is what makes a pitch detector genuinely useful for intonation work.
What should I do to get a stable reading? Sustain a single tone — a single note on an instrument or a sustained vowel — clearly and steadily. The tool requires a consistent pitched sound for at least 100–200 ms to produce a reliable F0 reading. Background noise, chord playing (multiple simultaneous notes), and very short or breathy tones all reduce detection reliability. A quiet room and a well-supported tone give the best results.
Does the tool work with any instrument? Yes — any instrument producing a clear, monophonic (single-note) tone in the 80–1,100 Hz range. This includes voice (all voice types), guitar, violin, cello, trumpet, clarinet, flute, piano (single note), and most other common instruments. Very low instruments (bass guitar, double bass, tuba) may produce less reliable results below approximately 80–100 Hz due to consumer microphone low-frequency roll-off.
Does the tool work on mobile? The tool functions on most modern mobile browsers. Chrome on Android generally works well. iOS Safari requires a user tap to unlock the AudioContext before microphone capture begins. For the most accurate pitch detection, desktop use with a wired microphone is recommended.
Understanding Your Results
What does “+12 cents” mean? Cents are a logarithmic unit for measuring pitch intervals. One semitone = 100 cents. One cent = 1/100 of a semitone. +12 cents means the detected frequency is 12 cents sharp of the nearest equal temperament note — sharp by slightly more than one eighth of a semitone. At A4 = 440 Hz, +12 cents corresponds to approximately 443.1 Hz. This is clearly perceptible to a trained musician and would typically require correction for professional performance or recording.
What does “A4 (−50 cents)” mean? The detected frequency is closest to A4 (440 Hz) but is 50 cents flat — which is exactly halfway between G#4/Ab4 and A4 in equal temperament. A result of ±50 cents consistently indicates either that the instrument is tuned to a non-standard reference pitch, that the instrument needs retuning, or that the detection pipeline is producing an error. Run the test again in a quieter environment to verify.
My reading keeps jumping between two notes. Why? Jump readings between two adjacent notes typically indicate one of two things: your pitch is sitting close to the midpoint between two notes (around ±50 cents), causing the “nearest note” label to alternate as the detected frequency fluctuates slightly; or background noise is causing frame-to-frame instability in the YIN detection. Try sustaining the tone more consistently and testing in a quieter environment.
The tool shows my note as an octave lower than I expect. Why? This is a YIN octave error. The YIN algorithm reduces but does not eliminate the tendency of autocorrelation-based detectors to return F0 at half the true frequency — one octave too low. This is more likely for tones with a very strong second harmonic (e.g. certain bowed string tones, some flute notes in the upper register), for tones at the very top of the detection range, and for signals with low SNR. If the displayed frequency is exactly half what you expect, the true F0 is one octave higher.
Why is my reading consistently flat by around 15–20 cents across all notes? A consistent flat offset across all notes typically indicates that your instrument or tuning reference is calibrated to a pitch standard other than A4 = 440 Hz. If your instrument is tuned to A4 = 432 Hz (sometimes called “philosophical pitch”), all readings will appear flat by approximately 31.7 cents. If you are using a DAW or software instrument set to a non-standard reference, this will produce a consistent offset. The tool is calibrated to ISO 16 (A4 = 440 Hz).
Accuracy and Limitations
How accurate is the pitch detection? Under typical conditions — a quiet environment, a sustained monophonic tone, and a functional consumer microphone — the tool achieves F0 detection accuracy of approximately ±2–5 cents in the range of 100–800 Hz. For frequencies below 100 Hz, accuracy may be ±5–15 cents due to consumer microphone low-frequency response limitations. Accuracy decreases further with background noise, OS audio processing, and inconsistent phonation.
Can this tool detect two notes played simultaneously? No. The YIN algorithm is a monophonic pitch detector — it is designed for a single fundamental frequency at a time. Playing a chord, a two-note interval, or two simultaneous tones will produce an unreliable result: the detector will return an F0 related to the interaction of the two frequencies, not a meaningful identification of either note individually. For chord detection, a dedicated polyphonic tool is required.
Does OS noise suppression affect the reading? Yes. Windows and macOS apply automatic gain control (AGC) and noise suppression to microphone input by default on many configurations. These processes alter the captured waveform in ways that affect the sharpness of the YIN difference function minimum, introducing additional uncertainty of 2–8 cents. Disabling these in your OS audio settings during critical pitch measurement can improve accuracy.
What is the perceptual threshold for pitch detection accuracy? Psychoacoustics research suggests that trained musicians can discriminate pitch differences of approximately 5–6 cents under optimal listening conditions. Untrained listeners typically require 15–25 cents of deviation to reliably perceive a pitch difference. The tool’s typical accuracy of ±2–5 cents is within the perceptual threshold for trained musicians — meaning small detection errors will be perceptible in a professional tuning context. For casual use and approximate tuning, ±5 cents accuracy is more than sufficient.
Is this tool accurate enough for professional tuning? For most professional tuning tasks — instrument setup, vocal warmup, intonation practice — the tool’s ±2–5 cents accuracy is adequate. For the highest-precision professional applications — such as calibrating electronic tuning equipment or verifying a pitch standard for recording — a dedicated hardware tuner or calibrated measurement instrument is recommended.
Technical Questions
What is the YIN algorithm? YIN (named after the Chinese concept of complementary duality) is a fundamental frequency detection algorithm developed by de Cheveigné and Kawahara (2002) and published in the Journal of the Acoustical Society of America. It uses an autocorrelation-based difference function that reduces the octave errors characteristic of standard autocorrelation, making it one of the most accurate general-purpose monophonic F0 detectors available. It is the algorithm used in this tool and is the standard reference algorithm in academic pitch detection research.
What is A4 = 440 Hz? A4 is the A note in the fourth octave of the standard musical scale. 440 Hz is the international standard reference pitch for A4, defined by ISO 16 (1975) and adopted by most orchestras, instrument manufacturers, and music software worldwide. Some ensembles and performers use non-standard references — 432 Hz, 415 Hz (baroque), 443 Hz (some European orchestras) — which will produce consistent cent offsets when measured against this tool’s 440 Hz calibration.
What is the cents system? Cents are a logarithmic unit for expressing pitch intervals, introduced by Alexander Ellis in the 19th century. The octave is divided into 1,200 cents (100 cents per semitone in equal temperament). Because the cents system is logarithmic, equal cent intervals represent equal perceived pitch differences across all frequency ranges — unlike Hz intervals, which are much larger in absolute terms at higher frequencies.
About This Website
Who runs OnlinePitchDetector.com? OnlinePitchDetector.com is built and maintained by Vincent Sullivan, audio signal processing educator. Vincent writes all content on the site personally. There are no guest contributors, no sponsored content, and no advertisers. For Vincent’s full background and the reasons this site was built, see the Author page.
Is this site free to use? Yes. The pitch detector and all educational content on OnlinePitchDetector.com are completely free. No registration, no account, and no payment of any kind is required.
How do I report an error or ask a technical question? Email contact@onlinepitchdetector.com with the subject line “Content Correction” for factual errors or “Technical Question” for measurement questions. Vincent reviews all submissions personally. Response time: 48–72 hours.
Written by Vincent Sullivan, founder of OnlinePitchDetector.com. Last updated: June 2026.