| String | Target Clearance (Over 1st Fret) |
Total Slot Height (From Fretboard) |
|---|
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Precision is everything in instrument setup, and the nut sits at the center of that precision. This small piece of bone, graphite or brass at the top of the neck controls how your strings sit across the lower frets and getting that height wrong throws off everything from playability to pitch accuracy.
A slot cut too shallow leaves the strings stiff and sharp-sounding. A slot cut too deep and you are fighting string buzz on every open note.
Most players and even some technicians have historically relied on approximations, charts or feel when cutting nut slots. This calculator was built to replace that approach with actual math tied to your specific instrument's geometry so you stop guessing and start cutting with confidence.
This tool is a web based measurement utility that generates precise, instrument-specific nut slot targets for every string on your guitar or bass.
Unlike printed reference charts that offer generic averages, this calculator takes the real physical dimensions of your fretboard and produces numbers that apply to your actual setup.
You input your first fret height, select your instrument type, and choose your preferred action level.
From there the calculator builds a complete slot-depth blueprint tailored to those inputs. It covers six string electric guitars, six-string acoustics and four-string bass guitars, and for every string it outputs two measurements: how much clearance should exist between the string and the top of the first fret and what the total slot depth should be measured from the bare fretboard surface.
Both numbers are provided so you can verify your progress no matter which measurement method your luthier tools support.
The nut's job sounds simple hold the strings at a fixed spacing and height at the headstock end of the neck. But the downstream effects of getting that height wrong are significant.
When you fret a note near the nut, you are physically pressing the string down to the fret wire. If the string starts too high, you are stretching it further than intended which increases tension and pulls the pitch sharp before the string even contacts the fret.
This is why a guitar can tune perfectly on open strings but sound off the moment you play a first position chord. The nut is almost always the reason.
From a feel standpoint a high nut makes the lower frets genuinely difficult to play. Gripping notes near the headstock requires more hand strength than it should which tires the hand quickly and discourages clean technique particularly for newer players.
On the other side, going too far when filing creates a different problem. Strings do not vibrate straight up and down. They move in an elliptical arc and if the slot sits too low, that arc carries the string into contact with the first fret even when no note is being fretted.
The result is a rattling, buzzing open string that kills sustain and produces an unpleasant clatter instead of a clean note.
There is no single correct answer that applies across all instruments and players. The right slot depth is determined by a combination of string gauge, scale length, instrument type and how physically hard the player attacks the strings.
Heavier strings vibrate in a wider arc, so they need more room to move without contacting the first fret. That is why the bass side of the nut always sits higher than the treble side the low E string on an acoustic needs considerably more clearance than the high E.
This calculator handles that graduated increase automatically, applying a progressive clearance scale from treble to bass strings.
Electric guitars generally tolerate tighter tolerances than acoustics because their strings operate under different tension and are typically played with a lighter touch.
Bass guitars sit at the opposite extreme, requiring the most generous clearances of the three to accommodate the large vibrational arc of heavy-gauge strings.
Step 1: Pick Your Unit of Measurement Start by selecting either inches or millimeters based on what your feeler gauges and calipers use. The underlying math is identical either way this setting just controls how results are displayed.
Step 2: Measure and Enter Your First Fret Height This single number drives the entire calculation. Use a digital caliper or carefully stacked feeler gauges to measure from the fretboard wood surface up to the top crown of the first fret wire. Enter that measurement exactly as-read into the input field.
Step 3: Select Your Instrument Choose between a 6-string electric, 6-string acoustic or 4-string bass. Each instrument type carries its own baseline clearance values, reflecting the real world differences in how strings on these instruments vibrate.
Step 4: Set Your Action Preference Select low, standard or high action based on your playing style. Players with a light, precise touch can comfortably use low action. Heavy strummers, aggressive pickers, and slide players should select high action to build in enough extra clearance that the strings do not buzz under aggressive playing.
Step 5: Read Your Results After clicking calculate, the results table fills in with two columns for each string. The Target Clearance value tells you the gap that should exist between the bottom of the string and the top of the first fret.
The Total Slot Height value tells you the complete distance from the fretboard wood to the bottom of the finished slot. Use whichever measurement method your tools and workflow favor.
Cutting nut slots is the last adjustment in a proper setup sequence not the first. If you file the nut before the neck geometry is correct your measurements will be wrong by the time the rest of the setup is dialed in.
The correct order is this: adjust the truss rod to achieve proper neck relief, then set the bridge saddle heights and match the saddle radius to your fretboard radius and only then measure and file the nut.
Any truss rod adjustment made after the nut is filed changes the geometry of the neck and invalidates the slot depths you worked to achieve. Always complete neck and bridge setup before touching the nut.
Use nut files that are sized to match the gauge of your strings. A file narrower than the string diameter will pinch the string and cause it to bind and ping during tuning changes. A file wider than the string will leave the slot loose letting the string rattle around inside.
Angle your file slightly downward toward the tuning machines as you cut. The goal is for the string to break cleanly over the front edge of the nut the edge closest to the frets.
If the highest contact point in the slot is anywhere other than that front edge the string will not seat properly and you will hear a sitar-style buzz even with correct measurements.
Work in small increments. Take a few filing strokes, seat the string, bring it to pitch and check the clearance with a feeler gauge.
This process takes longer but protects you from the most common and costly mistake in nut work: cutting too deep. Material that has been removed cannot be put back without replacing the nut entirely.
Not if you followed the correct setup order. Nut slot depth only influences string height across the first few frets and has no meaningful effect on bridge action further up the neck. If you set the bridge before the nut those measurements remain valid.
Yes and this is actually one of its most practical applications. When starting from a fresh, uncut blank whether bone, graphite or brass you need to establish every slot depth from zero. The calculator tells you exactly where the floor of each slot needs to land, giving you a clear target for the entire fitting process.
Baseline clearances are calibrated for a typical player. But someone who plays hard causes their strings to vibrate through a physically larger arc.
The action modifier adjusts each slot measurement by a small amount a few thousandths of an inch to match the larger or smaller envelope of motion produced by that player's specific attack preventing buzz at the extremes.
A great setup requires both careful technique and accurate numbers. Eyeballing the nut or relying on charts designed for an average instrument that may not match yours leaves too much to chance.
By entering the actual dimensions of your specific fretboard and your real playing preferences this calculator removes that uncertainty and gives you a slot depth target you can file toward with complete confidence.
Whether you are chasing ultra-low action for fast electric playing or building in generous clearance for hard acoustic strumming, the math will get you there as long as you file patiently and check your progress every step of the way.
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