How to Space Frets on the Fretboards of Acoustic Guitars

Getting the correct spacing between frets requires great accuracy.

The correct spacing of frets on the fingerboard of an acoustic guitar is essential to ensure the proper intonation of the instrument. If you're building your own acoustic guitar you'll need to find the right distance between all the frets so that when complete your guitar plays in tune. It's a job that calls for patience and accuracy but with care and attention, and the right tools and resources you can do a great job.

Things You'll Need

• Fret calculator
• Steel rule, marked in 1/100 inch
• Set square
• Sharp pencil, or sharp point scribe

Instructions

1. Measure the scale length of your guitar. This is the distance between the bridge on the guitar's body and the nut at the end of the neck. Check and double-check your measurement as this information is the basis of all other calculations.

2. Leave a straight edge on the fretboard so that you can be sure when you mark the the measurements that the frets will lie straight across. Fret measurements are always taken from the nut.

3. Divide your figure for scale length by 17.817 to get the position of your first fret. The result of this calculation for a scale length of 25.5 inches is 1.4312173 inches. Round the result to three decimal places, giving you 1.431 inches. Measure this distance from the front of the nut and mark a line with a very sharp pencil or sharp pointed metal scribe. Use the set square to get a perpendicular line.

4. Find the position of the second fret position by subtracting 1.431 inches from the overall scale length. Following the example above this would result in a figure of 24.069 inches. Divide this by the constant value of 17.817 to give 1.351 inches. Add this to the figure for the first fret to get 2.782 inches, and measure and mark the position of the second fret from the nut as for the first fret.

5. Calculate the third fret position by subtracting the total distance to the second fret and dividing by 17.817 as before. Add the result to the distance calculated for the second fret, and measure and mark from the nut as before. Continue in the same way until you have marked all fret positions on the fingerboard. Note that the position of the 12th fret should be exactly half the scale length.

Tips & Warnings

• Always measure the fret position from the nut to avoid introducing potential errors caused by rounding.

• It can be helpful to put a "zero fret" in front of the nut from which you can measure the fret spacing. The scale length in this case will be the distance from the zero fret to the bridge.

• There are many online tools to calculate fret positions for any given scale length that can make the job easier.

References

• Drexel University: Fretboard construction, Jonathan Sevy
• Build Your Guitar: Calculating fret distances

Resources

• Build Your Guitar: Fret Calculator