How to Measure Your Guitar's Action — and What the Numbers Should Actually Be
This is the question I get most once someone stops asking which guitar to buy and starts asking why the one they own fights them. "What should my action be?" It's a fair question with a slightly annoying answer: there is no single correct number. But there is a correct way to measure it, and a sensible range that covers most players. Once you can put a ruler on the thing and read a real figure, you stop guessing and start diagnosing — and you can tell a guitar that needs a ten-minute tweak from one that needs real work before you hand over money for it.
Here's exactly how I measure action on the bench, the numbers I aim for, and the mistakes that send people chasing problems that aren't where they think they are.
What "action" actually means
Action is just the height of the strings above the frets — how far you have to push a string down to make it ring. Low action feels fast and effortless but buzzes if you take it too far. High action is cleaner and louder acoustically but tiring to play and murder on your intonation up the neck. Everything in a setup is a negotiation between those two, and the number we use to talk about it is the string height measured at the 12th fret.
Why the 12th? Because it's the halfway point of the vibrating string, so it's the most honest single spot to judge the overall height. Measure too close to the nut and you're really measuring your nut slots; measure right at the bridge and everything looks fine even on a guitar that plays like a cheese slicer. The 12th splits the difference.
What you need to measure it
You don't need much. A small machinist's ruler marked in 64ths of an inch is the classic tool, and a purpose-made string action gauge (a little steel card with a stepped or notched edge) does the same job for about ten dollars. If you think in metric, any decent ruler with clear millimeter marks works — 1/64" is right around 0.4 mm, so the conversions are easy enough. Feeler gauges are for relief, which we'll get to. That's the whole kit.
Set the guitar up before you trust the number
Here's the part people skip, and it's the part that matters. You cannot read a meaningful action number on a guitar that isn't tuned to pitch and sitting in playing position. String tension pulls the neck into a bow, and that bow changes the height. So:
Tune to pitch first. Every measurement assumes the strings are at full tension in the tuning you actually play. Measuring a slack neck tells you nothing.
Hold it like you play it. Frets up, roughly vertical, on your lap or a stand. Laying a guitar flat on a bench can throw the reading off, because the neck sags differently.
Check the relief before you touch the action. Relief is the small forward bow in the neck, and it's a separate adjustment from height — it's the truss rod's job, not the bridge's. Capo the 1st fret, hold the low E down at the last fret, and look at the gap over the middle of the neck (around the 8th fret). You want a hair of daylight there — roughly the thickness of a business card, about .008"–.012" for most electrics. If the neck is dead flat or badly bowed, fix that first, because relief and action interact. A guitar with too much relief will read high at the 12th no matter how low you drop the saddles.
This is the single biggest reason people mis-diagnose a guitar. They call it "high action" when it's really a truss rod that needs a small turn, or they blame the bridge when only the first three frets buzz — which is almost always the nut, not the action at all.
The actual measurement
With the guitar tuned and the relief sane, measure the gap between the top of the 12th fret and the bottom of the string. Not the top of the fingerboard — the top of the fret wire. Do it for the low E and the high E; those two tell you almost everything, and you can eyeball the strings in between.
Rest the ruler on the fret next to the string (not on the string itself) and read where the underside of the string lines up. That's your number. Write down both sides — treble and bass are usually set a touch different, and that difference is deliberate.
The numbers I aim for
Here's where the factory specs are genuinely useful, because they give you a sane starting point that the manufacturers themselves consider "correct." Gibson sets a Les Paul at roughly 3/64" (about 1.2 mm) on the treble side and 5/64" (about 2.0 mm) on the bass side at the 12th fret. Fender's spec depends on the fretboard radius, which is the tell that radius and action are linked: a vintage 7.25"-radius board is set around 5/64" on both sides, a modern 9.5"–12" board around 4/64" (1.6 mm), and a flat 15"–17" board can go lower still, down toward 3/64" on the treble. Both brands publish these; they're not my invention.
| Setup | Treble (high E) at 12th | Bass (low E) at 12th |
|---|---|---|
| Low / shredder-friendly (flatter radius) | ~2.5/64" (1.0 mm) | ~3.5/64" (1.4 mm) |
| Middle of the road (Gibson/Fender factory-ish) | ~3–4/64" (1.2–1.6 mm) | ~4–5/64" (1.6–2.0 mm) |
| Higher / dig-in, slide, heavy strings | ~5/64" (2.0 mm) | ~6/64"+ (2.4 mm+) |
Treat the middle row as home base. If you play with a light touch and a flatter fretboard, you can creep lower before things buzz. If you dig in, bend hard, use heavier strings, or tune down, you'll want to sit higher. None of these are "right" or "wrong" — they're preferences, and the only judge that matters is whether the guitar plays clean everywhere you actually go on the neck.
Why the same number feels different on two guitars
This trips people up constantly: you set two guitars to identical 12th-fret heights and one feels lower. Usually it's the fretboard radius and the relief doing it. A flatter radius lets the whole string sit lower without choking out bends, so it feels lower at the same measured height. Taller frets change how far you press before the string beds down, too. So don't obsess over hitting a number to the thousandth — the ruler gets you in the ballpark; your hands make the final call. Its real value is consistency and diagnosis, not some magic figure.
Using this when you're buying a used guitar
This is where I lean on it hardest. When a used guitar comes across the bench, action is one of the first things I read, because it separates a quick fix from an expensive one. High action that drops to spec with a couple of saddle turns and a truss adjustment? No problem — that guitar just needs a setup. High action that won't come down because the saddles are already on the deck, or a bridge that's already bottomed out on a Tune-o-matic, is a red flag that points at neck angle or a warped neck — and those are real money. A ruler at the 12th fret, on a guitar tuned to pitch, tells you which situation you're looking at before you commit.
Every used guitar we sell gets set up on the bench before it goes out, so the action's already dialed in — but knowing how to read it yourself means you can keep it that way. You can see what's in stock here if you want something that arrives playing right.
FAQ
What is a good guitar action in mm?
For most electric players, roughly 1.2–1.6 mm on the treble side and 1.6–2.0 mm on the bass side at the 12th fret is a comfortable, clean starting point. Lighter players on flatter fretboards can go a little lower; heavy-handed players and drop tunings usually want a little higher.
Where exactly do I measure guitar action?
At the 12th fret, from the top of the fret wire to the bottom of the string, with the guitar tuned to pitch and held in playing position. Measure the low E and high E separately.
My low frets buzz — is my action too low?
Probably not. Buzz confined to the first few frets is almost always a nut that's cut too low or a neck that's too flat, not your overall action. Buzz spread across the whole neck is more likely an action or relief issue. Diagnosing where it buzzes tells you which adjustment to reach for.
Do I need to adjust the truss rod before checking action?
Check the relief first, yes. Relief is a separate adjustment from height, and if the neck has too much bow the 12th-fret reading will be high no matter what you do at the bridge. Set relief, then measure and set action.
Bench note: factory action figures cited here are Gibson's and Fender's own published starting specs; the wider comfort ranges are my own bench preferences and will vary with your radius, fret size, string gauge, and touch.
