How string tension works

The gist of it

Every string on your guitar is pulled tight to reach its pitch. This is the tension and is what makes a set feel loose and floppy or stiff and tight under your fingers. Three things push tension up:

• Heavier string: A thicker gauge weighs more per inch, so it needs more tension to reach the same note.
• Longer scale length: The distance from nut to bridge; longer scales stretch the string tighter.
• Higher pitch: Tuning up raises tension, tuning down lowers it.

To suggest string packs that feel right for your tuning, we calculate the tension of each string for the scale length of your guitar in order to reach the target pitch.

Before we get into the details...

You will constantly hear guitarists say "string gauge doesn't matter". This is true in a way and you only need to look at some artists and see what they prefer to use to understand that there is no right or wrong answer to string tension.

A few examples

• Lee Malia BMTH: Uses a .080 gauge on the bottom almost always. [Source]
• Fit For An Autopsy: Using a combination of packs and singles to achieve their desired tension 9-46 + 68 for Drop A, 10-52 + 74 for Drop G. [Source]
• Joe Bonamassa: Simply identifying how his setup can alter the feel of the string gauge itself. [Source]

The calculation

Tension follows a standard physics formula used across the industry (it's the same one Ernie Ball, D'Addario and others publish in their tension guides):

T

Tension, in pounds.

UW

Unit weight per inch of length (lb/in). This is the string.

L

Scale length, in inches.

f

Frequency of the target note, in hertz (e.g. standard A = 440 Hz).

386.4

A fixed gravity constant that converts the units into pounds of force.

This is run for every string in a pack, totalled up, and compared against a comfortable target range to score how well the pack fits your tuning.

Where the data comes from

The one value in the formula we can't derive ourselves is unit weight as it depends on how a string is actually built (core, winding, coating, materials). So we source it directly from each manufacturer's published data, gauge by gauge.

This matters because the same nominal gauge weighs slightly different amounts depending on who made it. Example:

When we know the brand of a pack, we use that brand's own unit weights so the estimate reflects the actual strings. If a brand hasn't published a weight for a particular gauge, we fall back to a D'Addario reference value for that gauge.

Everything here is an approximation

These numbers are a guide, not a lab measurement. Treat them as "close enough to compare packs," not gospel. A few reasons the real feel on your guitar may differ:

• When a brand's exact gauge weight isn't available, we substitute an average reference as a close stand-in.
• Results are rounded to two decimal places for display.
• Published unit weights vary slightly with manufacturing batch, coating, and materials.

Use the tension figures to compare sets and find a starting point, then trust your hands to make the final call.