String Gauge Tension Calculator

The standard string tension formula is T = (unit weight times (2 times length times frequency) squared) divided by the gravitational constant. With unit weight in pounds per inch, scale length in inches, and frequency in hertz, dividing by 386.4 (the acceleration of gravity in inches per second squared) gives tension in pounds. This is the same relation string makers publish.

Unit weight is the mass per unit length of the string, here expressed as pounds per inch. Thicker strings and denser materials have higher unit weight, so for the same pitch and scale they pull at higher tension. String manufacturers publish unit weight for each gauge; enter the value for your string.

Standard tuning frequencies come from equal temperament referenced to A4 at 440 hertz. For example, the low E string of a guitar (E2) is about 82.41 hertz. Enter the target pitch's frequency. You can use a tuner or a pitch-to-frequency reference for the note you are tuning to.

Scale length is the vibrating length of the string between nut and bridge. For a fixed pitch and string, a longer scale requires more tension, which is why long-scale basses feel tighter than short-scale ones at the same tuning. The tension rises with the square of the scale length.

The formula is exact for an ideal flexible string, and it matches published manufacturer charts closely when you use their unit weight values. Real strings have slight stiffness, so very heavy or short strings can deviate a little. Use measured unit weight for the best match.