String tension is determined by vibrating length, mass, and pitch. The string diameter alone does not determine a string’s tension. By using different raw materials (nickelplated steel or phosphor bronze, etc.) or by varying the ratio between the core and the wrap wire, two strings with the same diameter, tuned to the same pitch, could have two different tensions.
There are many factors other than string gauge that determine the actual and perceived string tension on your instrument:
• Scale length, or the distance between the nut and the saddle. The longer the scale, the higher the tension is for the same string tuned to the same pitch – for example, a standard Fender™ guitar at 25½” scale has more string tension and will feel stiffer than a standard Gibson™ 24¾” scale guitar, even if both are tuned to the same standard pitch.Some players adjust for this by using slightly heavier gauges on shorter scale guitar than on longer scale guitars.
Acoustic/Electric/Classical Guitar = 25 1/2”
Electric Bass Guitar (Superlong Scale) = 36”
Electric Bass Guitar (Long Scale) = 34”
Electric Bass Guitar (Medium Scale) = 32”
Electric Bass Guitar (Short Scale) = 30”
Mandolin = 13 7/8”
Mandola = 15 7/8”
Mandocello = 25”
Mandobass = 42”
Banjo = 26 1/4” (19 5/8” for 5th string)
• The flexibility of the instrument top and neck.
• The string break-angle at the nut and saddle/bridge.
• String height or “action” as adjusted at the saddle.
• Truss rod adjustment (neck relief).
Note: Before deciding on a string gauge, be sure your instrument is properly “set up.” Unusually high action can change the way the string tension feels and can also result in poor intonation.
How to Measure String Tension
String tension is measured in pounds of pull per string. When all of the tensions of each string are added up, you get the “set tension” for that set. If, for example, you want to change the tuning of one string, you should try to select a string gauge that will offer a similar tension to the string you are replacing, but can be tuned to the desired pitch.