Enter a string gauge, scale length, and target frequency to estimate the string’s tension in pounds.
String gauge (thousandths of an inch):
Scale length (inches):
Target pitch frequency (Hz):
How It Works
A vibrating string’s pitch depends on three things: how long it is, how heavy it is, and how tightly it is pulled. Guitar makers and string manufacturers use a well-known relationship to connect them. Rearranged to solve for tension, it looks like this:
T = (UW × (2 × L × f)²) ÷ 386.4
- T is the tension in pounds.
- UW is the string’s unit weight in pounds per inch. For a plain steel string, this comes from its gauge (diameter) and the density of steel, so it grows with the square of the gauge.
- L is the scale length in inches, the vibrating length from nut to bridge.
- f is the target pitch in Hz.
- 386.4 is the acceleration of gravity in inches per second squared, which converts mass to weight.
Worked example: a plain steel .010 string on a 25.5″ scale, tuned to high E (329.63 Hz), comes out at roughly 16 pounds of tension. That lines up with published charts for a standard light-gauge set. Move to a shorter 24.75″ scale at the same pitch and gauge, and the tension drops noticeably, which is why shorter-scale guitars often feel slacker.
Why String Tension Matters
Tension shapes how an instrument plays and sounds. Higher tension feels stiffer under the fingers, makes bending notes harder, and tends to give a tighter, more focused attack. Lower tension feels easier to fret and bend but can buzz against the frets and sound looser, especially when you dig in. Tension also matters for the instrument itself: a sudden jump to much heavier strings adds load to the neck, and it may call for a truss rod adjustment or a setup check.
This is why players check tension before switching to a drop tuning, changing gauges, or moving between guitars with different scale lengths. The goal is usually to keep the feel familiar while changing the pitch or the instrument.
How to Use This Tool
- Enter the string gauge in thousandths of an inch (for example, a high E string is often .010).
- Enter your instrument’s scale length, or leave the standard 25.5″ default.
- Enter the target pitch’s frequency in Hz and click Calculate.
This estimate is most accurate for plain steel strings; wound strings have a different effective unit weight per gauge and will actually pull somewhat higher than this estimate.
Did You Know?
- Total tension across all six strings of a standard-tuned acoustic guitar is often well over 150 pounds combined.
- Heavier gauge strings generally have more tension at the same pitch, which is part of why they can feel stiffer to fret.
Frequently Asked Questions
Does this work for bass strings?
The formula applies the same physics, but bass strings are almost always wound, so the plain-steel estimate here will read lower than the actual tension.
How do I find my note’s frequency in Hz?
Use the site’s Note & String Frequency Converter to look up the exact Hz for any note before entering it here.
Why is my result lower than the manufacturer’s chart?
Charts from string makers use each specific string’s measured weight, and most strings below the first two or three are wound. Wound strings carry extra mass in the wrap wire, so their real tension runs higher than this plain-steel estimate. For plain steel strings, the two should be close.
How does scale length change tension?
Longer scale lengths need more tension to reach the same pitch with the same string. That is why a 25.5″ scale guitar typically feels a little stiffer than a 24.75″ scale guitar with identical strings.
Can I use this to plan a drop or alternate tuning?
Yes. Look up the new frequency with the Alternate Guitar/Bass Tuning Frequency Calculator, enter it here with your string gauge, and compare the result to the tension at standard pitch. If it falls a lot, a heavier gauge can bring the feel back.