Guitar String Tension Calculator
Enter your scale length, string gauge, tuning and material to find the tension on each string in both pounds-force and Newtons. The calculator uses the standard physics formula adopted by D'Addario and other major manufacturers. Results update instantly as you type, and a bar chart shows the tension balance across all six strings.
Formula
Worked example
A Fender Strat (25.5 in scale) with a 0.010-inch plain steel string tuned to E4 (329.63 Hz): UW = pi/4 x 0.010^2 x 0.2835 = 0.00002222 lb/in. T = (2 x 25.5 x 329.63)^2 x (0.00002222 / 386.089) = 14.38 lbf (63.98 N).
What is guitar string tension and why does it matter?
String tension is the pulling force a string exerts on the guitar nut, saddle, neck and body when it is tuned to pitch. It determines how a string feels under the fingers - high tension strings feel stiff and require more force to fret or bend, while low tension strings feel loose and are easier to play but may buzz against the frets. Tension also affects tone: tighter strings tend to sound brighter and more sustaining, while looser ones often sound warmer and more responsive to light picking. Total tension across all six strings can range from around 80 lbf (356 N) for an extra-light acoustic set to over 180 lbf (800 N) for heavy electric sets or alternate tunings on long-scale instruments.
How the tension formula works
The standard formula used by D'Addario and most string manufacturers is T = (2 x L x f)^2 x (UW / g), where T is tension in pounds-force, L is scale length in inches, f is frequency in Hz, UW is the unit weight (linear density in lb/in), and g is the gravitational acceleration constant 386.089 in/s^2. Unit weight for a plain steel string is calculated from its diameter: UW = (pi/4) x d^2 x 0.2835, where 0.2835 lb/in^3 is the density of steel. Wound strings have additional mass from the winding material (nickel, phosphor bronze, brass), which this calculator accounts for by applying a per-material multiplier to the plain-steel unit weight at the same diameter. The formula shows that tension grows with the square of both scale length and frequency, so moving from 24.75 to 25.5 inches or raising pitch by a semitone each add roughly 6-9 % more tension.
Tension balance and how to choose the right set
A well-balanced string set has similar tension on every string, so the instrument plays consistently and the neck receives an even load. Standard factory sets are deliberately "unbalanced" in tension - the wound strings are often 20-40 % tighter than plain strings - because players and manufacturers have historically prioritised consistent tone rather than even feel. Specialty "balanced tension" sets (sold by companies like Stringjoy and D'Addario) try to equalize tension across all strings, which many players find more comfortable for bending and fingerpicking. You can spot an imbalance in this calculator by looking at the bars visual: if one string is dramatically taller than the others, swapping that string for a slightly lighter or heavier gauge will even out the set. The balance range output (highest minus lowest string tension) gives you a single number to minimize.
Scale length and alternate tunings
Every semitone you drop in tuning reduces tension roughly 11 % per string for the same gauge. So Drop D on the low string drops its tension by about 11 %, meaning a 0.052 gauge string in Drop D sits at roughly the same tension as a 0.046 in standard E. Players who tune to D Standard or C Standard often compensate by going up a gauge set to restore a familiar feel. Longer scale lengths have the opposite effect: a 27-inch baritone guitar at B standard produces similar tension to a 25.5-inch guitar at E standard with the same strings, which is why baritone instruments can use conventional gauges despite the lower pitch. This calculator lets you freely mix scale length, tuning and gauge to find the combination that feels right.
Common guitar scale lengths and tuning ranges
| Guitar model / type | Scale length (in) | Scale length (mm) | Typical use |
|---|---|---|---|
| Fender Stratocaster / Telecaster | 25.5 | 647.7 | Standard electric, bright tone |
| Gibson Les Paul / SG | 24.75 | 628.65 | Standard electric, warmer feel |
| PRS Custom 24 | 25 | 635 | Versatile, between Fender and Gibson |
| Baritone guitar | 27-28 | 686-711 | Drop tunings B or A standard |
| 3/4 travel guitar | 22-23.5 | 559-597 | Short-scale, lower tension |
| Classical guitar | 25.6 | 650 | Nylon string, light tension standard |
| Acoustic dreadnought | 25.4 | 645 | Steel string, medium tension |
| Extended-range 7-string | 26.5 | 673 | Adds low B, benefits from extra scale |
Scale length affects tension directly - longer scales produce higher tension for the same gauge and pitch.
Frequently asked questions
What is a good total tension for a guitar?
Most standard-braced acoustic guitars are designed for 130-170 lbf (578-756 N) of total string pull. Electric guitars are lighter and typically see 90-130 lbf (400-578 N). Going significantly above these ranges risks warping the top or neck over time; going well below them can cause tuning instability or a thin, lifeless tone. Your guitar's manufacturer documentation will list the maximum recommended tension if it exists.
How does string gauge affect tension?
Tension scales with the square of the string diameter. Moving from a 0.010 to a 0.011 plain string (a 10 % increase in diameter) raises tension by about 21 %, because (1.1)^2 = 1.21. This is why gauge jumps feel much bigger than the small number suggests. In practice, going up one standard gauge step (e.g., from .010 to .011, or .046 to .052) typically adds 10-20 % tension per string.
How much tension does tuning down add or remove?
Every semitone down lowers tension by roughly 11 %. Dropping from E4 to D4 (two semitones down) reduces string 1 tension by about 20 %. For Drop D on string 6, you lose one semitone worth of tension on just that string. Players who tune down a whole step often go up a gauge size (for example, from .010-.046 to .011-.052) to restore a similar feel.
Why do wound strings feel stiffer than plain strings at the same tension?
Stiffness (how hard a string is to push sideways or bend) comes from both tension and the string's resistance to bending, which physicists call "flexural rigidity." Wound strings have a stiffer core relative to their outer diameter, so they resist bending more than a plain string at the same tension. This is especially noticeable on the wound G string, which many players replace with a plain 0.017 to get a more even bend feel across strings 1-3.
Does string material affect tension?
Yes, slightly. Different winding materials have different densities, so a phosphor bronze wound string and a nickel-plated steel wound string of the same outer diameter have slightly different unit weights and therefore slightly different tensions. The difference is usually less than 5 % between common materials at the same gauge, but it is real and is accounted for by the material multiplier in this calculator.
What is unit weight (UW) and where can I find it?
Unit weight is the linear density of the string, measured in pounds per inch (lb/in) or kilograms per metre (kg/m). It encodes how much mass is packed into each inch of the string. D'Addario publishes unit weights for every string in their catalog in their annual Tension Guide PDF. For plain steel strings it can be calculated directly from the gauge and steel density; for wound strings it is measured from the manufactured product and varies slightly by manufacturer.