Correct intonation allows a guitar to play as accurately as practical across the fretboard by adjusting the effective speaking length of each string at the bridge.
The universal direction rule is simple: if the fretted note is sharp, lengthen the string; if it is flat, shorten the string. The mechanical procedure differs between bridge types, but that compensation principle does not.
In Brief
- Fretted note sharp: move the saddle away from the nut.
- Fretted note flat: move the saddle toward the nut.
- Retune the open string after every saddle movement before comparing again.
- Set strings, tuning, relief, action, bridge height and tremolo balance before final intonation.
- Extreme saddle positions can indicate a nut, fret, string, bridge-placement or setup problem rather than an intonation-screw problem.
In This Article
Intonation Fundamentals · Prepare the Guitar · Core Adjustment Method · Tune-O-Matic and Fixed Bridges · Tremolo Systems · When Intonation Will Not Set · Final Verification
Intonation Fundamentals
What Is Guitar Intonation?
The frets are positioned according to the instrument's nominal scale length.
In theory, the 12th fret divides that scale length into two equal parts and produces a note one octave above the open string.
In practice, pressing a string onto a fret increases its tension slightly.
This raises the pitch of the fretted note.
The saddle is therefore positioned slightly farther from the nut than the nominal scale-length point to compensate for this pitch increase.
The required compensation differs between strings because it is influenced by:
- String gauge
- String construction
- Plain or wound design
- Core-to-wrap relationship
- Tuning
- String action
- String stiffness
- Fretting pressure
This is why the saddles normally form a staggered pattern rather than a straight line.
What Intonation Adjustment Can Correct
Bridge intonation compensates for the pitch increase created when a string is fretted.
It can correct a consistent sharp or flat relationship between:
- The open string
- Its octave reference
- The fretted 12th-fret note
It cannot independently correct every possible tuning problem on a guitar.
Problems caused by the following may require a different solution:
- Excessive nut height
- Incorrect fret position
- Uneven frets
- Damaged strings
- Excessive action
- Incorrect neck relief
- Unstable tremolo balance
- Strong magnetic interference
- Incorrect bridge placement
- Unclear saddle contact points
Do not use extreme saddle positions to compensate for a fault elsewhere on the instrument.
When Should Intonation Be Checked?
Check intonation after:
- Installing a new bridge
- Installing new saddles
- Changing string gauge
- Changing string construction
- Changing the normal tuning
- Adjusting neck relief
- Changing string action
- Changing tremolo balance
- Changing bridge height
- Repairing the nut or frets
- Completing a general guitar setup
Intonation should be one of the final stages of the setup.
Prepare the Guitar
Complete the Mechanical Setup First
Before final intonation, establish:
- The intended string set
- The intended tuning
- Stable neck relief
- Final or near-final string action
- Correct bridge height
- Stable tremolo position where applicable
- Suitable pickup height
- Mechanically secure bridge hardware
Changing these variables later can change the compensation requirement.
The practical sequence is:
- Install the intended strings.
- Tune the guitar.
- Stabilize a floating tremolo where applicable.
- Set neck relief.
- Set string action and bridge height.
- Check nut and fret condition.
- Set pickup height to a suitable non-interfering position.
- Adjust intonation.
- Perform a final playing check.
Use the Intended Strings and Tuning
Set intonation with the string gauge, construction and tuning in which the guitar will normally be played.
Changing from one setup to another can alter:
- String tension
- Required saddle position
- Neck relief
- Bridge balance
- Playing pressure
- Compensation pattern
A guitar intonated in standard tuning is not automatically optimized for a substantially lower tuning.
A wound third string can also require a different saddle position from a plain third string of similar overall gauge.
Use Stable, Serviceable Strings
A damaged, corroded or unevenly worn string may produce inconsistent results.
For a reliable final setup, use strings that are:
- Mechanically undamaged
- Clean enough to vibrate consistently
- Correctly installed
- Stable at the intended tuning
New strings should be seated, gently stabilized and repeatedly retuned before final measurement.
Do not attempt final intonation while the strings are still changing pitch rapidly after installation.
Required Tools
Useful tools include:
- Accurate chromatic or strobe tuner
- Correct screwdriver
- Correct hex keys
- String winder
- Tremolo-specific saddle tool where applicable
- Good lighting
- Stable guitar support
The adjustment tool must fit the screw precisely.
An unsuitable tool can damage:
- Screw heads
- Hex sockets
- Threads
- Saddles
- Bridge finishes
Use a Consistent Measuring Method
For repeatable results:
- Hold the guitar in a normal playing position where practical.
- Use the same picking force for each reading.
- Allow the tuner display to settle.
- Fret directly behind the fret rather than midway between two frets.
- Use normal playing pressure.
- Avoid pressing the string down to the fretboard unnecessarily.
Fretting pressure can change the measured pitch significantly.
This effect becomes especially noticeable with:
- Tall frets
- Light strings
- Low-tension tunings
- Scalloped fretboards
- Strong fretting technique
The setup should reflect how the instrument is actually played.
Core Adjustment Method
Tune the Open String First
Tune the open string accurately to its intended pitch.
Always retune it after every saddle adjustment.
Moving the saddle changes the speaking length and tension relationship of the string.
A comparison made without retuning is not valid.
The 12th-Fret Harmonic
The 12th-fret harmonic provides an octave reference for the open string.
To produce it:
- Touch the string lightly directly above the 12th fret.
- Pluck the string.
- Remove the touching finger immediately.
- Allow the harmonic to ring clearly.
The harmonic does not require the string to be pressed to the fret.
It therefore does not include the pitch increase caused by fretting.
The Fretted 12th-Fret Note
After checking the open string or harmonic:
- Fret the string normally at the 12th fret.
- Pick it with similar force.
- Observe the stable tuner reading.
- Compare it with the octave reference.
The fretted note is the critical measurement because it includes:
- String displacement
- Added tension
- Actual fret height
- Action
- Player pressure
The harmonic alone cannot determine whether the saddle compensation is correct.
Open String vs. Harmonic
Both methods can provide a valid pitch reference:
Open String Method
Compare the accurately tuned open string with the fretted note one octave higher.
Harmonic Method
Compare the 12th-fret harmonic with the fretted 12th-fret note.
The harmonic method makes the octave comparison easy because both sounds are in the same pitch register.
In either case, the fretted note is the value that reveals the required compensation.
If the Fretted Note Is Sharp
When the fretted 12th-fret note is sharp:
- The compensated string length is too short.
- Move the saddle away from the nut.
- Retune the open string.
- Check the fretted note again.
Rule:
Sharp = lengthen the string
If the Fretted Note Is Flat
When the fretted 12th-fret note is flat:
- The compensated string length is too long.
- Move the saddle toward the nut.
- Retune the open string.
- Check the fretted note again.
Rule:
Flat = shorten the string
Basic Adjustment Cycle
For each string:
- Tune the open string accurately.
- Sound the 12th-fret harmonic or octave reference.
- Fret the string normally at the 12th fret.
- Determine whether the fretted note is sharp or flat.
- Move the saddle in the required direction.
- Retune the open string.
- Repeat the comparison.
- Continue until the best stable match is reached.
Make small adjustments.
Large movements can overshoot the required position and make the process unnecessarily difficult.
Do Not Follow Screw-Rotation Rules Blindly
The direction in which an adjustment screw must be turned depends on:
- Screw orientation
- Bridge construction
- Thread direction
- Saddle design
Do not rely on a universal instruction such as clockwise for sharp or counterclockwise for flat.
Watch the physical movement of the saddle.
The only universal direction rule is:
- Sharp: move the saddle away from the nut.
- Flat: move the saddle toward the nut.
Tune-O-Matic and Fixed Bridges
Intonating a Tune-O-Matic Bridge
A Tune-O-Matic bridge uses one longitudinal adjustment screw for each saddle.
Depending on the bridge design, the screw heads may face:
- The pickups
- The tailpiece
There is no universal screw-facing rule for every Tune-O-Matic bridge.
Manufacturers intentionally produce both reverse and non-reverse versions.
To adjust a Tune-O-Matic saddle:
- Tune the string.
- Check the fretted 12th-fret note.
- Determine the required physical direction.
- Turn the correct intonation screw in a small increment.
- Confirm that the saddle moved in the intended direction.
- Retune the open string.
- Recheck the fretted note.
If the screw does not move freely, stop.
Do not damage the screw head or force the saddle against string pressure, corrosion or the end of its channel.
Reducing string tension may be necessary before further adjustment.
Tune-O-Matic Bridge Orientation
Bridge orientation influences:
- Adjustment-screw access
- Available saddle travel
- Saddle contact position
- String clearance
- Retaining-wire position
Do not turn the complete bridge around merely because another guitar has its screws facing the opposite direction.
The correct orientation depends on the actual bridge and its saddle arrangement.
Reversing Tune-O-Matic Saddles
Some Tune-O-Matic saddles are intentionally reversible.
The original Gibson bridge patent describes reversible saddles as a method of increasing the available adjustment range.
Reversal changes the location of the saddle's string-contact edge relative to its adjustment screw.
Before reversing a saddle, confirm:
- The saddle design permits reversal.
- The string slot remains correctly oriented.
- The string leaves from a clear contact edge.
- The saddle remains properly retained.
- The adjustment screw remains functional.
- The string path behind the saddle remains unobstructed.
A saddle should be reversed only to obtain useful adjustment range.
It should not be reversed solely to create a visually uniform arrangement.
Saddle Reversal Is Not a Universal Repair
Reversing a saddle may provide additional travel, but it cannot correct:
- Incorrect bridge placement
- Wrong scale geometry
- A damaged string
- Excessive action
- An unsuitable nut
- A badly positioned fret
- An incompatible bridge
When several saddles remain at the end of their travel, inspect the complete guitar geometry.
Saddle Contact Point
The intonation position is defined by the point where the speaking length of the string ends at the saddle.
That contact should be:
- Clear
- Stable
- Correctly located
- Free from multiple competing edges
Possible problems include:
- Saddle slot sloping toward the nut
- Burrs
- Deep wear
- Multiple contact points
- String touching an adjustment screw
- String touching another bridge surface
An unclear contact point can make tuner readings inconsistent.
KMS Finished V-Shaped Saddle Contacts
KMS V saddles and FlowTrem2 saddles center the string through finished V-shaped geometry rather than through a conventionally filed slot.
The intonation principle remains unchanged:
- Sharp: move the V-saddle away from the nut.
- Flat: move the V-saddle toward the nut.
Do not file a conventional string slot into a finished KMS V-shaped contact.
Changing the intended contact geometry can affect:
- String centering
- Contact definition
- Radius
- Gauge flexibility
- Intonation reference
KMS ONE and Vintage ONE Bridges
Each string is intonated individually through its corresponding saddle.
During adjustment:
- Use the correct tool.
- Observe the physical saddle movement.
- Retune after every adjustment.
- Do not force a saddle at the end of its travel.
- Follow the product-specific instructions for any locking components.
A locking mechanism should secure the completed setup.
It should not be used to pull a saddle, bridge or post into an incompatible position.
Individual-Saddle Fixed Bridges
Modern fixed bridges commonly allow each saddle to move independently.
The procedure remains:
- Tune the string.
- Compare the octave reference and fretted note.
- Move the saddle toward or away from the nut.
- Retune.
- Recheck.
Some saddles also have individual height screws.
After changing the longitudinal position, verify that the saddle:
- Remains level where intended
- Has not changed height unintentionally
- Does not rock
- Retains adequate screw engagement
- Follows the required string radius
Three-Saddle Telecaster-Style Bridges
A traditional three-saddle Telecaster bridge supports two strings on each saddle.
Moving one saddle therefore changes the effective length of both strings in that pair.
With a straight shared saddle, both strings cannot be positioned longitudinally completely independently.
The practical process is:
- Tune both strings in the pair.
- Check both fretted octave notes.
- Move the shared saddle.
- Retune both strings.
- Compare both results.
- Establish the best practical balance.
Compensated saddles use angled, stepped or separately defined contact geometry to provide a different speaking length for each string of the pair.
They reduce the compromise without changing the basic intonation method.
Normal Saddle Pattern
On a six-string guitar, the final saddle arrangement often appears as two related compensation groups:
- Plain strings
- Wound strings
A visible step often occurs at the transition between them.
The exact pattern depends on:
- Whether the third string is plain or wound
- Gauge
- Construction
- Tuning
- Action
- Scale length
Do not position saddles according to appearance alone.
A visually unusual pattern can be correct.
A familiar-looking staircase can be wrong.
Tremolo Systems
Floating Tremolo Systems
A floating tremolo balances string tension against spring tension.
Moving one saddle and retuning one string can slightly change the equilibrium of the entire bridge.
Before final intonation, confirm:
- Intended strings are installed.
- Guitar is in its intended tuning.
- Spring balance is established.
- Tremolo rests at its intended neutral position.
- Neck relief and action are set.
During the process:
- Tune all strings.
- Check one string.
- Adjust its saddle.
- Retune the complete guitar.
- Recheck the tremolo position.
- Recheck the adjusted string.
- Continue with the next string.
Do not intonate a floating system while its neutral position is still changing.
Double-Locking Tremolos
A conventional Floyd Rose Original requires a different mechanical adjustment procedure because each saddle is clamped to the baseplate.
Floyd Rose specifies:
- Leave the nut clamps released.
- Tune all strings with an electronic tuner.
- Compare the 12th-fret harmonic and fretted note.
- Determine the required saddle direction.
- Loosen the string until it is slack.
- Hold the saddle in position.
- Loosen its mounting screw.
- Move the saddle by a small amount.
- Retighten the mounting screw.
- Retune the string.
- Recheck the intonation.
- Repeat until correct.
- Retighten the nut clamps after completion.
Do not attempt to slide a fully clamped saddle along the baseplate.
Floyd Rose Saddle-Mounting Holes
On the Floyd Rose Original, the saddle-mounting screw can be repositioned into another baseplate hole when additional adjustment range is required.
Floyd Rose specifies that:
- A forward hole may be used when the saddle cannot move farther toward the nut.
- A rearward hole may be used when the saddle must move farther away from the nut.
The screw must still clamp the saddle securely.
This instruction is specific to compatible Floyd Rose constructions.
Do not assume that every licensed double-locking tremolo uses the same hole pattern.
Intonation Tools for Double-Locking Tremolos
A compatible intonation tool can provide controlled saddle movement while the mounting screw is released.
Floyd Rose describes The Key as fitting over the String Lock Screw and providing fine control of an Original Floyd Rose saddle after the Saddle Mounting Screw has been loosened.
Use only a tool designed for the exact tremolo.
A tool must not:
- Damage the String Lock Screw
- Interfere with fine tuners
- Pull against a fully tightened saddle screw
- Replace secure final tightening
KMS FlowTrem2
The same fundamental intonation rule applies:
- Sharp fretted note: increase string length.
- Flat fretted note: decrease string length.
For saddle release, positioning and final tightening, follow the current FlowTrem2 product instructions.
Do not transfer torque values, saddle-hole positions or special-tool procedures from another double-locking tremolo without confirming that they apply to the FlowTrem2.
When Intonation Will Not Set
When a Saddle Reaches the End of Its Travel
Do not force the adjustment screw beyond its intended range.
When correct intonation cannot be reached, check:
- Saddle orientation
- Bridge orientation
- Available saddle travel
- String gauge
- String construction
- Tuning
- Neck relief
- String action
- Nut condition
- Saddle contact point
- Bridge placement
- Scale length
- Tremolo position
- Condition of the string
One saddle reaching its limit may indicate an unusual string or setup requirement.
Several saddles reaching the same limit may indicate a more fundamental geometry or setup problem.
Nut Height Can Resemble an Intonation Problem
A high nut slot requires the string to be pushed farther down at the first few frets.
This increases tension and can make lower-fret notes noticeably sharp.
Typical symptoms include:
- Open string is correctly tuned.
- First-position notes are sharp.
- Error is strongest near the nut.
- Error becomes less pronounced farther up the neck.
- Excessive pressure is required near the first fret.
Moving the bridge saddle cannot independently correct this lower-fret geometry without changing the result elsewhere.
Inspect the nut before using an extreme saddle position to correct sharp first-position chords.
Compensated Nuts
Some manufacturers use compensated nut geometry to improve pitch accuracy, particularly in the lower frets.
A compensated nut changes the effective starting point of individual strings.
This demonstrates an important distinction:
- Bridge compensation adjusts the speaking length at the bridge.
- Nut compensation changes the effective string origin.
- The two solve different parts of the tuning system.
A guitar equipped with a manufacturer-designed compensated nut should be intonated according to that manufacturer's procedure.
Neck Relief and Action
Higher action requires the string to travel farther before reaching the fret.
This creates more stretching during fretting and can increase the compensation requirement.
Excessive relief can also produce unnecessarily high action in part of the neck.
Set relief and action before final intonation.
Do not lower or lengthen every saddle merely to disguise an unsuitable neck setup.
Fret Condition and Position
Bridge intonation assumes that the frets provide accurate and consistent reference points.
Problems can result from:
- High frets
- Low frets
- Uneven wear
- Flat fret crowns
- Poorly defined crown positions
- Incorrectly positioned frets
A saddle adjustment affects the entire string.
It cannot correct one isolated fret without affecting all other notes on that string.
When one fret is consistently incorrect while surrounding frets are acceptable, investigate the fret rather than the saddle.
Fretting Pressure
A tuner measures the pitch produced by the complete playing action.
It cannot determine whether a sharp note was caused by:
- Incorrect saddle position
- Excessive finger pressure
- Pressing too far behind the fret
- Pulling the string sideways
- Tall frets
- Scalloped fingerboard geometry
Use consistent pressure throughout the setup.
After technical adjustment, test the guitar with the player's normal technique.
Pickup Magnetic Pull
Strong magnetic pull from pickups positioned too close to the strings can disturb string vibration.
Possible symptoms include:
- Unstable tuner display
- Warbling
- Irregular overtones
- Notes that do not settle clearly
- Problems strongest on particular strings or frets
Pickup height should already be within a suitable working range before final intonation.
When readings remain unstable, temporarily increase the string-to-pickup distance and test again.
Damaged or Unstable Strings
Suspect the string when:
- One string produces inconsistent readings.
- The required saddle position changes repeatedly.
- A new setup behaves correctly except for one string.
- The string is visibly damaged.
- The winding is distorted.
- The string has a kink at the saddle or tuner.
- The pitch changes irregularly during decay.
Replace the questionable string before changing bridge geometry or modifying the instrument.
Saddle Slot and Contact Problems
The speaking length should terminate at one clearly defined saddle point.
Inspect for:
- Burrs
- Wear
- Multiple contact edges
- Incorrect slot slope
- Excessively deep slot
- Loose saddle
- String contacting an adjustment screw
- String contacting another bridge surface
Do not file, polish or reshape a saddle without understanding:
- Its intended geometry
- Material
- Coating
- String-contact design
KMS V-saddles should not receive conventional filed slots.
String Contact Behind the Saddle
The saddle should remain the defined bridge endpoint of the speaking string length.
Contact behind the saddle does not automatically change the fretted scale length, but unwanted secondary contact can cause:
- Mechanical noise
- Friction
- String wear
- Unstable movement
- Interference with adjustment screws
- Ambiguous vibration behavior
Inspect the path toward the tailpiece or string anchor.
Correct significant interference before finalizing the setup.
Final Verification
Check More Than the 12th Fret
Use the 12th fret as the primary adjustment reference.
Afterward, check musically relevant positions across the fretboard, including:
- Lower-position chords
- Mid-neck chords
- Upper-register single notes
- Notes commonly used by the player
Additional fret checks are diagnostic.
Do not repeatedly move the saddle to chase a different reading at every fret.
A standard straight-fret guitar uses one bridge compensation position per string and remains a practical compromise influenced by:
- String stiffness
- Nut geometry
- Fret placement
- Action
- Playing pressure
- Equal temperament
The goal is the best stable musical result across the usable fretboard.
Intonation and Equal Temperament
Correct bridge intonation does not mean that every interval and every chord will be acoustically pure.
Standard guitars normally use equal-tempered fret placement.
Equal temperament distributes tuning differences so that the instrument can play in all keys.
Some intervals may therefore beat slightly even when the guitar is correctly set up.
Do not confuse the normal behavior of tempered tuning with a defective bridge.
Why Intonation Changes Over Time
The required saddle positions can change after:
- String replacement
- Gauge changes
- Alternate tuning changes
- Neck-relief movement
- Action adjustment
- Tremolo rebalancing
- Saddle replacement
- Nut or fret work
- Bridge movement
Seasonal neck movement may indirectly alter intonation by changing relief and action.
Recheck the basic setup before moving the saddles.
How Accurate Should the Result Be?
Aim for the closest stable match obtainable under normal playing conditions.
Do not chase every momentary tuner fluctuation.
Evaluate:
- Stable portion of the note
- Repeatability
- Normal fretting pressure
- Musical performance across the neck
A highly sensitive tuner can display variations caused by:
- Pick attack
- Finger pressure
- String decay
- Vibrato
- Temperature
- String condition
The most precise-looking number is not necessarily the most repeatable playing result.
Final Intonation Procedure
After all saddles have been adjusted:
- Tune every open string accurately.
- Check every 12th-fret harmonic.
- Check every fretted 12th-fret note.
- Use consistent pressure.
- Recheck the complete tuning.
- Confirm saddle screws are secure.
- Check that every saddle remains stable.
- Inspect the string path.
- Test chords near the nut.
- Test chords in the middle of the neck.
- Test upper-register notes.
- Recheck a floating tremolo's neutral position.
- Lock the nut where applicable.
- Complete final tuning with the fine tuners.
- Perform a normal playing test.
Common Intonation Mistakes
Avoid:
- Adjusting intonation before relief and action
- Using unstable or damaged strings
- Forgetting to retune after moving a saddle
- Fretting with excessive pressure
- Following clockwise or counterclockwise rules blindly
- Adjusting from the harmonic alone
- Forcing a resistant adjustment screw
- Sliding a locked tremolo saddle
- Ignoring floating-tremolo balance
- Positioning saddles according to appearance
- Trying to correct nut height at the bridge
- Ignoring fret problems
- Ignoring pickup magnetic pull
- Forcing a saddle beyond its travel
- Reversing a saddle without checking its geometry
- Modifying a KMS V-saddle
- Assuming every licensed tremolo uses the Floyd Rose Original procedure
When Professional Assistance Is Recommended
Professional assessment is advisable when:
- Several saddles reach the end of their travel.
- The bridge appears incorrectly positioned.
- Lower-fret notes remain excessively sharp.
- Frets are uneven or badly worn.
- The tuner reading remains unstable.
- Saddle screws or threads are damaged.
- A double-locking tremolo cannot be balanced.
- Structural bridge relocation may be required.
- Nut or fret work is necessary.
- The cause of the pitch problem cannot be identified.
Do not modify the guitar body until strings, setup, hardware and measurement technique have been ruled out.
Quick Reference
Fretted note sharp
Move the saddle away from the nut.
Fretted note flat
Move the saddle toward the nut.
After every saddle movement
Retune the open string.
Lower frets sharp but octave acceptable
Inspect nut height and fretting pressure.
Reading unstable
Inspect the string, pickup distance, contact points and tremolo balance.
Saddle at its limit
Check the entire setup and bridge geometry before modifying anything.