Reading a Chromatic Tuner: What Cents Mean
A chromatic tuner tells you two things: which note you're closest to, and how far you are from it. That second number is measured in cents, and understanding it is the difference between chasing the needle around and tuning quickly. This guide explains what the cents readout actually measures and how this site's tuner displays it.
What a cent is
A cent is one hundredth of a semitone — the distance between two adjacent frets on a guitar, split into 100 equal steps. An octave contains 12 semitones, so it spans 1,200 cents. The scale is logarithmic: each cent multiplies the frequency by the same tiny ratio rather than adding a fixed number of hertz. That design matches how human hearing works — we perceive pitch by ratios, not by raw frequency differences. A note 10 cents sharp sounds equally out of tune whether it's a low bass note or a high one.
Why the needle is not a Hz readout
Because cents are ratios, the same cents error corresponds to very different frequency errors at different pitches. Take the two E strings on a guitar, both drawn from standard tuning: low E is E2 at 82.41 Hz, and high E is E4 at 329.63 Hz — two octaves apart. Being 5 cents sharp on the low E means being about 0.24 Hz high. Being 5 cents sharp on the high E means being about 0.95 Hz high — four times the frequency error, but the same needle position and the same perceived out-of-tuneness.
This is why a good tuner displays cents rather than hertz: one scale that means the same thing everywhere on the instrument. If a tuner showed "+1 Hz," you'd have no idea whether that was nearly perfect (on a low string) or badly sharp (on a high one).
How this tuner displays it
The tuner on this site compares the pitch it detects against the nearest note in equal temperament, referenced to A4 = 440 Hz, and shows the difference on a needle:
- The needle spans ±50 cents. Fifty cents is half a semitone — the point at which you're closer to the next note than the one displayed. Any error larger than that clamps to the end of the scale, because past that point the tuner re-labels your pitch as the neighboring note instead.
- The "Tuned" band is ±5 cents. When the detected pitch is within 5 cents of the target, the display reads Tuned. Outside that band it tells you the direction to move: Tune up when you're flat (negative cents), Tune down when you're sharp (positive cents).
Why ±5 cents and not zero? A vibrating string isn't a laboratory oscillator — its pitch wavers slightly as the note decays, and the attack of a pluck reads sharper than the sustain. Most listeners can't reliably hear errors under about 5 cents in normal playing, and chasing the last cent means fighting noise in both the string and the measurement. Landing inside the band is in tune for any practical purpose.
Sharp, flat, and the tune-up habit
Flat means below the target pitch (needle left, negative cents); sharp means above it (needle right, positive cents). When you're flat, tighten the string toward the pitch. When you're sharp, don't just nudge it down to the line: drop below the target deliberately, then come back up to it. Approaching every string from below keeps the string, nut, and tuning gears loaded in one direction, so the pitch doesn't slip the moment you start playing. It's the single habit that most improves tuning stability.
Let the note ring while you read the needle — pluck once, watch the sustain, and ignore the first instant of the attack. Repeated hard picking while turning the peg gives the tuner (and your ear) a moving target.
Put it to use
Open the tuner, play a string, and watch the cents readout as you adjust. If you want the exact target notes and frequencies for guitar, ukulele, or Bb trumpet, they're tabulated in the Standard Tuning Reference.