How to Set Your Guitar's Intonation With Just a Tuner
How to Set Your Guitar's Intonation With Just a Tuner
Here's the short version, because it's genuinely this simple: intonation is just making sure each string plays in tune all the way up the neck, and you fix it by moving the bridge saddle for that string forward or back until the 12th-fret harmonic and the 12th-fret fretted note read the same on a tuner. That's the whole job. A clip-on tuner and a screwdriver will get you there.
I set intonation on nearly every guitar that comes across the bench before it goes out the door, and it's one of the few setup jobs I actively encourage players to learn themselves. It's low-risk, it's reversible, and once your open strings are in tune but that big open G chord still sounds slightly off up around the 5th fret, this is almost always the reason why.
Diagram: the 12th-fret intonation test, the entire method on one page.
What bad intonation actually sounds like
People expect a badly intonated guitar to sound dramatically wrong. It rarely does. What you get instead is a guitar that tunes up perfectly with the open strings, sounds fine on the first couple of frets, and then feels a little sour as you move up — chords that don't quite lock in, an octave that sounds tense, a high B or G string that seems to fight you no matter how carefully you tune. If you've ever thought "this guitar just doesn't sound right and I can't say why," intonation is the first thing I'd check.
The reason it happens is unavoidable physics. Pressing a string down to the fret stretches it a tiny bit sharp, and the thicker or higher off the board a string sits, the more it stretches. Compensating for that at the saddle is what intonation is.
Do these three things first
This is the step most people skip, and it's why their intonation "won't hold." Intonation depends on the neck and the string height being right, so you set it last, not first. The accepted order for a setup is relief, then action, then intonation, and there's a good reason for it: neck relief changes string height, and string height changes the effective length of the string, so if you intonate and then adjust either one, you've undone your own work.
Before you touch a saddle:
- Put on fresh strings and stretch them in. A dead, worn string reads inconsistently and can throw the whole exercise off. Old strings are the single most common reason a guitar won't intonate cleanly.
- Check your neck relief and set your action. If you've recently raised or lowered the action, or adjusted the truss rod, do that first and let the neck settle.
- Tune to pitch and hold the guitar in playing position. Flat on a bench with the neck unsupported reads differently than upright the way you actually play. Intonate the way you play.
The 12th-fret test, step by step
Work one string at a time, low E to high E. For each one:
- Tune the open string dead-on with your tuner.
- Play the harmonic at the 12th fret — touch the string lightly directly over the fret, don't press it down — and note where the tuner sits. This is your reference.
- Now fret the note at the 12th fret with normal playing pressure and read the tuner again.
- Compare the two. If the fretted note matches the harmonic, that string is done. If it reads sharp or flat, you've got an adjustment to make.
A quick honesty note: you can also just compare the open string to the fretted 12th-fret octave, and for most players that's close enough. The harmonic-versus-fretted method is a hair more precise because both notes are the same octave, which is why it's the one I use. Either way, the fix is identical.
Which way do I move the saddle?
This is the part everyone second-guesses, so here's the rule worth memorizing: a sharp fretted note means the string is too short — move the saddle back, away from the nut, to lengthen it. A flat fretted note means the string is too long — move the saddle forward, toward the nut, to shorten it.
Diagram: sharp means lengthen the string, flat means shorten it.
The way I keep it straight in my head: if the fretted note is too high, I need more string, so the saddle moves away. Make small adjustments — a quarter to a half turn of the screw at a time — then retune the open string and re-check the 12th fret, because moving the saddle also nudges your open tuning. It's a back-and-forth, and it's normal to take a few passes per string.
Your bridge decides how you turn the screw
The concept is universal; the hardware isn't. What you're turning depends entirely on what bridge your guitar has.
A Strat-style bridge from a Fender Player II we had in stock. Each of the six saddles has its own intonation screw at the back edge; turning it slides that one saddle forward or back.
On a Fender-style bridge (Strat, Tele) each saddle has a spring-loaded screw at the rear. Turn it clockwise and the saddle generally moves back toward the screw; counter-clockwise and it moves forward. A Telecaster with vintage three-saddle brass barrels is the exception — two strings share one saddle, so it's always a compromise and you get it as close as you can.
A Tune-o-matic bridge on a Gibson Les Paul Standard from the shop. The row of small screws across the bridge sets each saddle's position.
On a Gibson Tune-o-matic, each saddle rides on a small screw across the top of the bridge. Here's the honest bit I won't fake for you: which direction a given screw moves the saddle depends on which way the bridge is oriented and where the screw heads face, and it varies. So don't memorize a direction — make a small turn, look at which way the saddle actually slid, and go from there. On wraparound bridges and many budget hardtails, per-string adjustment is limited or nonexistent; some are pre-compensated at the factory and simply can't be dialed in string by string, which is worth knowing before you go hunting for screws that aren't there.
The mistakes I see most
The big one is intonating on old strings and wondering why it drifts. The second is doing it with the guitar flat on a table instead of in playing position. The third is chasing perfection — if you're within a couple of cents at the 12th fret across all six strings, stop. A guitar is an equal-tempered compromise by design, and past a certain point you're adjusting for a precision your ears will never hear. If a string simply refuses to intonate no matter what you do, that's usually a flag pointing somewhere else: a worn nut, a high fret, or a saddle that's hit the end of its travel. That's the point where it's worth bringing it to a tech.
FAQ
How often should I set my intonation?
Any time you change string gauge, after a truss rod or action adjustment, and as a quick check at a seasonal setup. If you keep the same strings and the same action, it stays put for a long time.
Does string gauge really change intonation?
Yes. A heavier or lighter set changes string tension and thickness, which changes how much each string stretches when fretted. Switch gauge and you'll almost always need to reset intonation.
Can I set intonation with a phone tuner app?
You can, and it'll be a real improvement over ignoring it. A good clip-on or pedal tuner reads a little steadier and faster, which makes the back-and-forth less fiddly, but the method is exactly the same.
My guitar is in tune open but chords sound off higher up — is that intonation?
Most of the time, yes, and this test will tell you in about five minutes. If the 12th-fret check comes back clean and it still sounds sour, look at the nut next.
Every used guitar we sell gets a proper setup and intonation check before it ships, so what you play is what we heard on the bench. You can browse what's in stock in our guitars in stock collection.
