Guitar String Tension Calculator
Calculate guitar string tension in pounds, kilograms and newtons from the gauge and string type or the unit weight, the scale length and the tuned note — for one string or a whole set in any tuning, or find the gauge that gives the tension you want.
How it works
Tension (lb) = unit weight (lb/in) × (2 × scale length (in) × frequency (Hz))² ÷ 386.09 · in SI: T (N) = μ (kg/m) × (2 × L (m) × f)² · kg-force = N ÷ 9.80665 · plain steel unit weight = 0.282 lb/in³ × π × gauge² ÷ 4 · note frequency = A4 × 2^((n − 69) ÷ 12)
A vibrating string’s pitch is set by its length, its mass per unit length (the unit weight) and how hard it is stretched, so for a given scale and note the tension follows directly from the unit weight: T = μ(2Lf)². In inches and pounds the constant 386.09 (standard gravity in in/s²) turns pound-mass into pound-force; string makers often round it to 386.4, which changes results by under 0.1%. You can enter the unit weight from any tension chart, or pick a string type and gauge: plain steel is computed from the density of music wire, and nickel-plated and phosphor bronze wound strings use D’Addario’s published unit weights, interpolated between listed gauges. The full-set mode adds up all six or seven strings in standard, drop or open tunings, shows each string’s tension so you can balance the set, and gives the total pull on the neck. The find-gauge mode works backwards from the tension you want. Retuning, a non-440 reference pitch and tables of how tension changes with tuning and scale length show why down-tuned guitars use heavier strings and baritones need longer scales.
Worked example
A nickel-wound .046 low-E string has a unit weight of 0.00038216 lb/in. On a 25.5" scale tuned to E2 (82.41 Hz): tension = 0.00038216 × (2 × 25.5 × 82.41)² ÷ 386.09 = 0.00038216 × 4,202.91² ÷ 386.09 ≈ 17.5 lb (7.9 kg, 77.8 N). A whole 10–46 set in standard tuning pulls about 16.2 + 15.4 + 16.6 + 18.4 + 19.5 + 17.5 ≈ 103.6 lb on the neck. Tuned down a whole step to D2, the same low string drops to about 13.9 lb, roughly 21% less.
Sources: D’Addario — String Tension Pro and string tension specifications · stringcalc — D’Addario unit-weight data (plain steel, nickel wound, phosphor bronze)
Frequently asked questions
Where do I find the unit weight?
From the string maker’s tension chart — D’Addario, for example, lists the unit weight (lb/in) of every single string. If you only know the gauge, choose “By gauge” and the string type: plain steel is calculated from its density and wound strings use chart values. Wound strings of different alloys and core sizes vary by a few percent between brands.
What is a normal string tension?
Electric guitar strings in standard tuning usually sit around 13–20 lb each, about 95–110 lb for a 10–46 set. Acoustic strings run higher, roughly 16–30 lb each and 140–170 lb for a set. A balanced set keeps every string close to the same tension so they feel alike under the fingers.
How does tuning down change tension?
Tension depends on frequency squared, so each semitone down cuts it by about 11%, and a whole step (two semitones) by about 21%. That is why drop and down-tuned guitars use heavier gauges or longer scales to keep a firm feel.
Why do heavier strings feel stiffer?
To reach the same note, a string with more mass per inch must be pulled tighter — tension rises directly with unit weight and with the square of scale length and pitch. That extra tension is the stiffer, higher-effort feel of a heavier gauge.
Can I use this for bass or other instruments?
The physics is the same for any string, so the unit-weight mode works for bass, ukulele or piano wire if you enter the right unit weight and scale. The gauge mode uses guitar string charts; bass strings have different core and wrap designs, so use the maker’s bass unit weights for them.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.