Calculate equal guitar nut slot spacing and string center positions for any nut width and string count.
Measure the height of your frets using a feeler gauge. Enter the string gauge and desired 'clearance' over the first fret.
The tool provides the target depth for each slot. A standard 'safe' clearance is 0.010" for the low E and 0.006" for the high E.
Check depth frequently while filing; removing too much material will cause incurable open-string buzzing and requires nut replacement.
It subtracts both edge margins from the nut width and splits the remainder into equal center-to-center steps: gap = (width − 2 × margin) ÷ (strings − 1). Each string center then sits at margin + n × gap, measured from the nut edge.
A 43 mm nut carrying 6 strings with a 3 mm edge margin yields a 7.40 mm center-to-center gap, placing the string centers at 3.00, 10.40, 17.80, 25.20, 32.60 and 40.00 mm across the nut.
It is the distance from each end of the nut to the center of the outermost strings. Enlarging it pulls the outer strings inward and tightens the whole layout: on a 43 mm nut, going from 3 mm to 3.5 mm margins narrows the gap from 7.40 mm to 7.20 mm.
The tool computes equal center-to-center spacing, where every string center is the same distance from its neighbors. Proportional layouts — which equalize the air gaps between string edges by accounting for each string's diameter — follow a different scheme that this calculator does not model.
The underlying math is defined for any instrument with at least two strings, since spacing has no meaning for one, and the input form covers common 4- to 12-string configurations.
Three numbers, all in millimeters: the width of the nut blank (form range 20–80 mm), the number of strings, and the edge margin (0–10 mm). The resulting gap and every string-center position are reported to two decimal places.