Calculate truss rod turns needed to correct neck relief. Enter measured and desired relief to get the exact number of quarter-turns.
Enter the relief you measured and the relief you want, both in millimeters, plus how much relief one full turn of your rod removes (the tool defaults to 0.25 mm per turn, a sensible figure for a typical single-action rod). Measure relief by capoing the first fret, holding the last fret, and reading the gap at the 7th–8th fret; most electric necks play best with 0.2–0.4 mm there.
The calculator subtracts desired from measured relief and divides by the per-turn figure, rounding to the nearest quarter turn. Correcting a bowed-up neck from 0.5 mm to 0.2 mm is a 0.3 mm change — 1.25 turns clockwise to tighten the rod and pull the neck straighter. A smaller 0.4→0.2 mm correction is just 0.75 of a turn clockwise.
Direction follows the sign of the difference: a positive gap (too much relief) calls for clockwise tightening, while a back-bowed neck reading 0.1 mm against a 0.3 mm target needs 0.75 turn counter-clockwise to loosen. Differences under 0.02 mm are treated as already within tolerance, so no adjustment is suggested. Always turn in small steps, retune, and let the neck settle before re-measuring.
The calculator defaults to 0.25 mm of relief change per full turn, a reasonable figure for a typical single-action rod. Stiffer necks, double-action rods and different thread pitches move more or less, so measure your own neck's response over a couple of turns and enter that value for the most accurate result.
Most electric guitars play best with 0.2–0.4 mm of relief, measured at the 7th fret while capoing the 1st fret and holding the last fret down. Flatter setups buzz on hard playing; more relief raises action and hurts intonation.
If you measure more relief than you want — say 0.5 mm against a 0.2 mm target — the 0.3 mm difference needs 1.25 turns clockwise to tighten the rod and pull the neck straighter. A back-bowed neck reading 0.1 mm against a 0.3 mm target is the opposite case: 0.75 turn counter-clockwise to loosen and let relief return.
Truss rods respond in small increments and overshooting is easy, so the calculator rounds to the nearest quarter turn — a practical step you can actually dial in by feel. Differences under 0.02 mm are reported as within tolerance, meaning no adjustment is needed. Always retune and let the neck settle for a few minutes between adjustments before re-measuring.