Rulers, not mics
Guitar calculators
The fret calculator uses the twelfth root of two. Distance from the nut to fret n is the scale length times one minus two to the power of minus n over 12. The gaps shrink as you go up the neck. The tension calculator uses published unit weights, scale length and frequency. Same gauge, lower pitch, less pull.
Tools in this section
Fret calculator
Distance from the nut and the gap from the previous fret, for 24.75, 25, 25.4, 25.5 or 27 inch scales, in inches or millimetres. Optional pitch at each fret.
String tension calculator
Estimate tension from a published unit weight, scale length and frequency. Formula: UW times (2 × L × F) squared, divided by 386.4. Compare two pitches on the same string.
Why the math is separate from the tuner
A tuner tells you what is sounding now. These pages tell you what a fretboard or a string would do on paper. Use the fret table when you are comparing 24.75 and 25.5 inch scales, or checking a number a luthier already quoted. Use tension before you buy a heavier low string for drop D. Neither result is a measurement of your guitar.
Units
Scale length can be inches or millimetres. Tension comes out in pounds and newtons. The unit weights are historical D'Addario chart figures in pounds per inch, labeled as such, not a promise about the set in your hand.
Questions
- Do I need the mic?
- No. If the fields are filled, the table is already the answer.
- Can this replace a setup ruler?
- It gives the equal-tempered ideal. A worn fingerboard or a misplaced nut will not match the table, and the page cannot see that.