In this lesson
Intonation describes how closely a guitar’s fretted notes match their intended pitches. A guitar can have its open strings in tune while notes farther up the neck sound sharp or flat.
Scale length is a design measurement that determines the fret spacing. On a conventional, single-scale guitar with an uncompensated nut, twice the distance from the nut’s fretboard-side string contact point to the centre of the twelfth-fret wire gives the nominal scale length. A compensated nut needs its own manufacturer’s measuring guidance. The parts of a guitar lesson identifies the nut and bridge.
The actual contact point at each bridge saddle allows for compensation: a small change in vibrating string length to account for the string and the effect of fretting it. The saddles need not all sit at the same distance from the nut, and the twelfth fret need not be the exact halfway point of each compensated open string.
Guidance source-checked on 2 November 2026. The photograph is retained from the original lesson.
Check the setup first
Use strings in good condition, in the gauge and tuning you intend to play. Let new strings settle according to the manufacturer’s guidance. Check the setup in the order specified for your instrument before fine-tuning intonation: neck relief, action and a floating bridge’s balance can all matter. The truss rod lesson explains relief and why it should be measured before an adjustment.
Use a tuner capable of showing small pitch differences. Hold the guitar in its normal playing position and use a consistent picking and fretting touch. Excessive fretting pressure can pull a note sharp. Worn strings, nut or fret problems, or a pickup set too close can also make a useful comparison difficult.
Compare the twelfth-fret notes
Follow your manufacturer’s checking method. A common method compares the natural harmonic near the twelfth fret with the note fretted at the twelfth fret:
- Tune the open string accurately.
- Sound its twelfth-fret natural harmonic by touching lightly and releasing the touch as it rings. Check the pitch.
- Fret the same string at the twelfth fret with a normal playing grip, without bending it sideways, and check that pitch.
- Repeat the comparison to see whether the difference is consistent.
The harmonic and fretted note should be close to the same pitch, an octave above the open string. A ruler can help establish an initial saddle position, but it cannot replace this pitch comparison. Fender calls its measuring stage a rough preset and checks the sounding notes during final adjustment.
What the comparison tells you
For a bridge with an individually adjustable saddle, the usual correction is:
| Fretted twelfth-fret note compared with the harmonic | Saddle movement for the usual correction |
|---|---|
| Sharp: higher in pitch | Away from the nut, increasing the vibrating length. |
| Flat: lower in pitch | Towards the nut, decreasing the vibrating length. |
This describes saddle travel. The screw to use, its turning direction, the tool and whether to slacken the string depend on the bridge. Identify those details in its manual before making a change. Retune and recheck after each small adjustment using the specified procedure.
An acoustic saddle or a bridge shared by several strings may not offer a separate screw for each string. Some designs use a pre-compensated contact surface. Leave saddle filing, nut work and changes to an unfamiliar bridge to a repairer.
Floyd Rose and other locking tremolos
Identify the exact bridge model before releasing any lock. Saddle attachment screws, string-clamping screws and fine tuners perform different jobs. Do not use a rear string-clamping screw as an improvised handle for pushing or pulling a saddle.
Floyd Rose’s published procedure slackens the string before releasing the saddle’s attachment screw, then secures the saddle and retunes before checking again. Other systems differ: Ibanez publishes separate procedures for Edge/Lo-Pro Edge and Edge-Zero/ZR-2, the latter using a dedicated intonation-adjustment bolt. A similar appearance does not make their controls interchangeable.
Use the labelled instructions for your bridge, including any required tool, lock-release, string-tension and reassembly steps. If you cannot identify a control or keep the saddle securely clamped, stop and ask a repairer. Also stop if the required movement exceeds the available travel, a fastener resists or the readings remain inconsistent.
Check the result across the neck
After retuning, play notes and chords in several positions with your usual touch. Matching one twelfth-fret comparison does not guarantee that every chord will sound perfectly in tune. If a problem persists at particular frets or strings, have the whole setup checked instead of repeatedly moving the saddle.