Guitar & Bass String Tension Calculator

A string under tension is a length of wire or wound wire trying to vibrate at a specific frequency, and the physics connecting gauge, scale length, and pitch to that tension is exact and well understood. The wave equation for a vibrating string says the frequency it wants to ring at depends on its length, the tension pulling it taut, and how much mass it has per inch of length (its "unit weight"). Flip that relationship around and you can solve for the one variable players actually care about: how hard is this string pulling on my neck right now, in pounds or kilograms?

For a plain steel string — the high E and B strings on most electric guitars — the unit weight calculation is exact, not an estimate. A string is a cylinder, so its cross-sectional area is π×(diameter/2)², and steel has a well-established density of about 0.284 pounds per cubic inch. Multiply the two and you get pounds of mass per inch of string, no guesswork involved. That is why a 0.010-inch high E string at a 25.5-inch scale length tuned to standard E4 lands right around 16 lbs of pull — a number you can independently verify with nothing more than a ruler, a micrometer, and the formula shown alongside every result here.

Wound strings — nickel-wound electric strings, phosphor bronze acoustic strings, and roundwound bass strings — are a different story, and this calculator is honest about it. A wound string has a steel (or other) core wrapped in a separate wire, so its mass depends on both the core's diameter and the wrap wire's material, thickness, and winding density, none of which show up in a simple outer-diameter measurement. Rather than pretend a wound string is a solid rod of one uniform material, this tool applies a documented effective-density multiplier — roughly 1.5 to 2 times a solid steel core of the same outer diameter — to approximate the extra mass the wrap adds. It is clearly labeled as an approximation everywhere it appears, because presenting it as exact would be dishonest about what the numbers actually mean.

Why does any of this matter to a working player? Because tension, not just gauge number, is what your neck actually feels. Jumping from a 0.009 set to a 0.011 set, or tuning a 0.010 set down a whole step, changes the net pull on the neck by several pounds per string — sometimes enough to need a truss-rod adjustment, a different bridge spring tension, or a fresh setup entirely. Knowing the tension in advance, in real units, turns a string change from a guess into a calculation.