Stewart Macdonald Fret Calculator

Professional grade precision for luthiers and instrument builders

Total Calculated Frets: 22

Distance Nut to 1st Fret: 1.431

Remaining Scale After Last Fret: 7.250

Fret #	From Nut	Fret to Fret

What is the Stewart Macdonald Fret Calculator?

The stewart macdonald fret calculator is an essential precision tool used by luthiers, guitar technicians, and hobbyist instrument builders to determine the exact placement of frets along a fingerboard. Accurate fret placement is the single most critical factor in ensuring a stringed instrument plays in tune. Even a fraction of a millimeter of error can lead to poor intonation and “sour” notes.

While often associated with the famous supply company, the math behind a stewart macdonald fret calculator relies on the physical laws of equal temperament. Whether you are building a custom electric guitar, a mandolin, or a ukulele, calculating the distance from the nut to each fret is the first step in the construction process.

Common misconceptions include the idea that fret spacing is “linear” or that all guitars use the same scale. In reality, the stewart macdonald fret calculator must be adapted for every unique scale length, as the distance between frets shrinks mathematically as you move closer to the bridge.

Stewart Macdonald Fret Calculator Formula and Mathematical Explanation

The calculation is based on the 12th root of 2, which is approximately 1.059463. However, luthiers traditionally use the “Rule of 17.817”. This constant is derived from the physics of vibrating strings and ensures that each fret increases the pitch by exactly one semitone.

The formula for calculating the distance of any fret (n) from the nut is:

Distance from Nut = Scale Length – (Scale Length / (2 ^ (n / 12)))

Alternatively, to calculate the distance to the next fret relative to the remaining length:

Distance to Next Fret = Remaining Scale Length / 17.817

Table 1: Variables in Fret Calculation

Variable	Meaning	Unit	Typical Range
Scale Length	The total vibrating length of the string	Inches / mm	24″ – 34″
Fret Number (n)	The specific fret being calculated	Integer	1 – 24
17.817	The standard luthier constant	Constant	Fixed

Practical Examples (Real-World Use Cases)

Example 1: Classic Fender Scale (25.5″)

If you are building a Stratocaster-style guitar, you enter 25.5 into the stewart macdonald fret calculator. For Fret 1, the calculation is 25.5 / 17.817 = 1.431″. The 12th fret will be exactly 12.75″ from the nut. Using these precise measurements ensures that the guitar maintains perfect intonation across all octaves.

Example 2: Short Scale Gibson (24.75″)

For a Les Paul style build, the scale length is shorter. Entering 24.75″ into the stewart macdonald fret calculator yields a 1st fret distance of 1.389″. This closer spacing is what gives short-scale guitars their distinct “slinky” feel and reduced string tension.

How to Use This Stewart Macdonald Fret Calculator

1. Select your Scale Length: Enter the intended vibrating distance between the nut and the bridge.
2. Define Fret Count: Input how many frets your fingerboard will have (standard is 21, 22, or 24).
3. Choose Units: Switch between Inches and Millimeters depending on your measuring tools.
4. Review the Table: The stewart macdonald fret calculator generates two columns: “From Nut” (cumulative) and “Fret to Fret” (individual spacing).
5. Mark Your Board: Use the “From Nut” measurements for the highest accuracy, as measuring fret-to-fret can lead to cumulative “creep” errors.

Key Factors That Affect Stewart Macdonald Fret Calculator Results

• Scale Length Selection: This determines the overall tension and tonal brightness. Longer scales generally offer more “snap.”
• Temperature and Humidity: Wood expands and contracts. Always calculate and mark your fretboard in a climate-controlled environment.
• Bridge Compensation: The stewart macdonald fret calculator provides theoretical positions. Bridges are usually moved back slightly (compensated) to account for string stretching when fretted.
• String Gauge: Heavier strings may require slightly different compensation, though the physical fret slots remain fixed.
• Nut Material: The starting “zero” point must be perfectly square and accurately slotted for the calculator’s results to hold true.
• Fretboard Radius: While the calculator handles the linear distance, the curvature of the board affects how you physically cut the slots.

Frequently Asked Questions (FAQ)

Does the Stewart Macdonald Fret Calculator account for compensation?

No, the stewart macdonald fret calculator provides the mathematical fret positions. Bridge compensation is added during the final setup phase by moving the bridge saddles slightly farther from the nut.

Why is the 12th fret always at the halfway point?

In equal temperament, an octave is exactly double or half the frequency. Mathematically, this means the 12th fret must sit at exactly 50% of the scale length.

Can I use this for a Bass guitar?

Absolutely. The stewart macdonald fret calculator works for any stringed instrument, including bass (usually 34″), ukuleles, and banjos.

What is “Fret Creep”?

Fret creep happens when you measure the distance from one fret to the next individually. Small errors in each measurement add up. It is always better to measure every fret from the nut (zero point).

Is 17.817 the only constant used?

Historically, some used 18, but 17.817 is the modern standard for the most accurate musical intervals. Our stewart macdonald fret calculator uses the more precise 12th root of 2 formula.

What if I want a multi-scale (fanned fret) guitar?

For fanned frets, you must run the stewart macdonald fret calculator twice: once for the treble scale length and once for the bass scale length, then connect the points.

Does string height (action) affect fret placement?

High action requires more compensation at the bridge because the string stretches more when pushed to the fret, but the physical location of the fret on the wood does not change.

Should I calculate in MM or Inches?

Most professional luthiers prefer Metric (mm) for the stewart macdonald fret calculator because it is easier to read fine increments like 0.01mm on digital calipers compared to fractions of an inch.