Build calculator · 02
String tension
calculator.
How hard is that set actually pulling? Set your scale length and tuning, pick gauges, and find out before you build a baritone that feels like a rubber band.
25.5 Fender · 24.75 Gibson · 27 baritone · 34 bass
Most players find 15 to 20 lb per string comfortable on an electric. Under 13 feels slack and buzzes; over 24 is stiff and hard on the neck.
What the number means
Tension is what your left hand is fighting and what your neck is holding back. A standard set of tens on a 25.5″ guitar in standard tuning pulls roughly 100 pounds in total, and each string lands somewhere between 15 and 20 pounds. That range is not a rule handed down from anywhere, it is simply where several decades of players have converged, and your hands may prefer something else.
Three things move the number
- Gauge. Tension goes up with the square of the diameter, so a small jump in gauge is a big jump in pull. Going from tens to elevens adds around 20% per string, not 10%.
- Pitch. Also squared. Dropping from E to D takes roughly 20% of the tension straight out.
- Scale length. Squared again. This is why a 27″ baritone in B feels normal while a 24.75″ guitar in B feels like tuning down a floor tom.
Planning a down-tuned build
The usual mistake is to buy a heavier set and hope. Do it the other way round: pick the tension you want, then work backwards to the gauge. If your standard set sits at 17 lb on the low string and you want the same feel in drop C, this calculator will show you which gauge gets you back there at your scale length.
For anything below C standard, consider a longer scale before a heavier gauge. Very thick strings on a short scale sound dull and intonate badly, because a stiff string does not behave like the ideal flexible one the physics assumes.
The formula
T = ( UW × (2 × L × F)² ) ÷ 386.4
Where T is tension in pounds, UW is the string's weight per inch in pounds, L is the scale length in inches and F is the frequency in hertz. The 386.4 converts to consistent units.
On accuracy. Plain steel strings are calculated directly from steel's density and are accurate to well under a percent. Wound strings depend on the ratio of core to wrap, which varies between manufacturers, so those figures use a general approximation that lands within roughly 3% of published charts. That is fine for choosing a set. If you are designing hardware around a specific load, use the unit-weight figures from your string maker's own chart.
What all this does to the neck
Around 100 pounds of pull bends the neck forward into relief. The truss rod fights it. Change your set or your tuning significantly and the relief changes with it, which is why a new gauge always means a fresh setup, new relief, new action, new intonation, and sometimes wider nut slots. Budget an hour, not five minutes.
What this does not do
Calculated tension is a physical estimate. Core construction, winding method, flexibility, and manufacturer tolerances can make two strings with similar tension feel different.
Last reviewed: August 2026
What to do with the numbers
Compare the strings to each other before looking only at the total. A balanced set does not require identical tension, but one string that is far outside the group will usually feel and respond different.