Guitar String Tension Calculator

Tension in this formula is proportional to the square of frequency, so raising pitch by a given percentage raises tension by roughly twice that percentage -- a half-step increase (about a 6% frequency change) produces roughly a 12% tension increase, not 6%. This squared relationship is also why tuning up multiple steps or switching to a much higher tuning without also adjusting gauge can push a string's tension well past its safe range even though the pitch change feels modest.

Scale length is squared in the tension formula just like frequency, while gauge only enters through unit weight, which is proportional to gauge squared but is otherwise a smaller multiplier in the overall equation -- in practice, moving from a short scale to a long scale guitar changes tension more per percentage point than an equivalent percentage change in gauge. That's why switching a string set between a short-scale and long-scale instrument at the same tuning can move tension noticeably even with identical strings.

It checks whether the computed tension in pounds falls between 5 and 40 lbs, a broad range that covers typical properly-tuned steel guitar strings without being tight enough to flag every reasonable setup as unsafe. It is a rough sanity check, not a manufacturer spec -- a string genuinely close to its rated breaking tension can still fall inside this range, so always cross-check against the specific string's published tension rating before committing to an unusual tuning or gauge combination.

Different materials pack a different mass into the same gauge -- steel, nickel-wound, and phosphor bronze strings are all denser than nylon, so a nylon string of the same numerical gauge weighs meaningfully less per inch and therefore requires less tension to reach the same pitch at the same scale length. This is why a classical guitar strung with nylon at a similar scale length to a steel-string acoustic sits at dramatically lower string tension for the same tuning.