Guitar Tuner
Tune your guitar by microphone or by ear for standard EADGBE, with the reasons a guitar never quite plays in tune everywhere.
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A perfectly tuned guitar is still out of tune
Pure intervals are simple frequency ratios — an octave 2:1, a fifth 3:2, a major third 5:4. Equal temperament divides the octave into twelve identical steps instead, so everything except the octave lands slightly off. In cents, a hundredth of a semitone:
| Interval | Pure | Equal | Error |
|---|---|---|---|
| octave | 1200.0 | 1200 | 0.00 |
| perfect fifth | 702.0 | 700 | -1.96 |
| perfect fourth | 498.0 | 500 | +1.96 |
| major third | 386.3 | 400 | +13.69 |
| minor third | 315.6 | 300 | -15.64 |
| major sixth | 884.4 | 900 | +15.64 |
| minor seventh | 996.1 | 1000 | +3.91 |
| major second | 203.9 | 200 | -3.91 |
The fifth is within two cents, which almost nobody detects. The major third is nearly fourteen cents sharp — well inside what an ordinary ear notices, and why a held major chord has a faint beating in it that a barbershop quartet singing pure ratios does not.
It cannot be fixed, because the circle does not close
Stack twelve pure fifths and you should land back where you started, seven octaves up. You do not: (3/2)12 is 129.746 while 27 is 128. The gap is 23.46 cents, the Pythagorean comma. It is not a rounding error or a limitation of instruments — it is a fact about the numbers.
You cannot have pure fifths and pure octaves at once, so some compromise is compulsory. Equal temperament spreads the comma evenly, costing each fifth exactly 23.46 ÷ 12 = 1.96 cents, and in exchange every key sounds identical. Earlier tunings piled the whole error into one place, which made several keys sweeter than equal temperament and one unusable.
Which is why the G and B strings sound sour
| Strings | Interval | Error |
|---|---|---|
| E to A | perfect fourth | +1.96 cents |
| A to D | perfect fourth | +1.96 cents |
| D to G | perfect fourth | +1.96 cents |
| G to B | major third | +13.69 cents |
| B to E | perfect fourth | +1.96 cents |
Standard tuning is four perfect fourths, a major third, then another fourth. Four of the five gaps are off by two cents. The G-to-B gap is the major third, off by 13.69 — seven times worse than any neighbour. That one pair carries almost all the tuning error on the instrument, and it is exactly the pair guitarists retune by ear most often without knowing why.
In hertz: with A at 440, the equal-tempered fifth above is 659.26 Hz where a pure one would be 660 — 0.74 Hz apart. Small, and the beating is audible on a sustained chord.
How to use
- Allow microphone access, or use the reference tones.
- Tune each string, always ending by tuning up to pitch.
- Retune after the first pass — strings pull each other.
- Check tuning at the fifth and seventh frets as well as open.
Frequently asked questions
What is standard tuning?
E, A, D, G, B and E from lowest to highest, with A above middle C at 440 hertz as the usual reference. The interval between the G and B strings is a third while all the others are fourths, which is a compromise that makes chord shapes playable and scale patterns slightly irregular.
Why should I always tune up to the note?
Because it takes up the slack in the tuning machine and settles the string against the nut. Tuning down leaves the mechanism loose, and the string tends to drift sharp again as it settles. Overshooting slightly and coming back up is the standard technique.
Why does the guitar go out of tune as I tune it?
Because the neck flexes under total string tension, so tightening one string slightly changes the others. Two or three passes are normal, and a substantial change — like moving to a different tuning — needs several, plus time for the neck to settle.
Why does my guitar sound out of tune up the neck?
Because of intonation, which is set by the position of each saddle. If a string plays sharp at the twelfth fret relative to its harmonic, the saddle needs moving back. Fretting also stretches the string slightly sharp, which is why heavy-handed players sound sharper.
Is a guitar ever truly in tune?
No, and this is a genuine property of the instrument rather than a fault. Equal temperament makes every key equally usable by making none of them perfectly in tune, and the fixed frets mean compromises everywhere. Some players and makers use compensated nuts or fanned frets to reduce it.
Does the microphone tuner work in a noisy room?
Less reliably. It listens for pitch, and background noise, other instruments or a nearby amplifier confuse it. Playing one string cleanly and letting it ring, close to the microphone, gives the most stable reading — and a clip-on tuner sensing vibration is better in a band setting.
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