# Guitar String Tension Calculator (D’Addario Unit Weights)

URL: https://speedycalculator.com/calculators/other/guitar-string-tension/
Last updated: 2026-10-30

> The guitar string tension calculator finds the tension of a string from the scale length, the note it is tuned to and the string type and gauge, using D'Addario's published unit weights. It also works backwards from a target tension to the right unit weight and gauge.

## Inputs

- Scale length (in, cm, mm, m, ft)
- Pitch
- Note
- Octave — Standard guitar tuning: E2 A2 D3 G3 B3 E4; bass: E1 A1 D2 G2.
- Frequency (Hz, kHz)
- Calculate
- String type
- String gauge (diameter) (in, mm) — e.g. 0.010 for a “10” high E, 0.046 for a low E in a 10–46 set.
- Unit weight (lb/in, kg/m, g/m)
- Target tension (lb, kg, N)

## Results

- String tension
- Unit weight used
- Frequency
- Nearest note
- Unit-weight source
- Closest gauge
- Nearest gauges in this string type
- How it feels
- Tension of every gauge of this type at this pitch and scale

## Formula

```
T = μ × (2 × L × f)²   (μ in kg/m, L in m, f in Hz → T in N)
T (lb) = UW (lb/in) × (2 × L (in) × f)² ÷ 386.09
f of a note = 440 × 2^((MIDI − 69) ÷ 12)
```

## Explanation

A vibrating string obeys Mersenne's law: its frequency is f = (1 ÷ 2L) × √(T ÷ μ), where L is the vibrating length, T the tension and μ the mass per unit length (unit weight). Turned around, the tension needed to reach a pitch is T = μ × (2Lf)². Tension grows with the square of both the scale length and the frequency – tuning a string up a whole tone raises its tension by about 26%, and a 25.5″ guitar needs about 6% more tension than a 24.75″ one for the same strings.

The unit weight depends on gauge, material and construction (plain steel, round, half-round or flat wound, nylon, bronze or nickel wrap), so it is best taken from the manufacturer's tables. This calculator embeds D'Addario's published unit weights for twelve string families: plain steel, XL nickel-plated round wound, stainless round, half-round and flat wound, phosphor bronze (round and polished), 80/20 and 85/15 brass, clear nylon, silver-plated wound nylon and electric bass nickel round wound. Gauges not in the table are interpolated.

Use it to design a balanced set, check what happens in drop or baritone tunings, or choose gauges for a different scale length.

### How to use the Guitar String Tension Calculator

- **Scale length**
- **Pitch**
- **Note**
- **Octave** — Standard guitar tuning: E2 A2 D3 G3 B3 E4; bass: E1 A1 D2 G2.
- **Frequency**
- **Calculate**
- **String type**
- **String gauge (diameter)** — e.g. 0.010 for a “10” high E, 0.046 for a low E in a 10–46 set.
- **Unit weight**
- **Target tension**

Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.

### How it works

The note and octave give the frequency with A4 = 440 Hz (or enter any frequency). The tool looks up the unit weight for the string type and gauge in D'Addario's table (lb/in), converts it to kg/m and computes T = μ(2Lf)². In target mode it solves μ = T ÷ (2Lf)² and lists the nearest D'Addario gauges.

### Worked example

A D'Addario .010 plain steel string (PL010, unit weight 2.215 × 10⁻⁵ lb/in = 3.9555 × 10⁻⁴ kg/m) tuned to E4 = 329.63 Hz on a 25.5″ (0.6477 m) scale: 2 × 0.6477 × 329.63 = 427.0 m/s, squared 182,330, times 3.9555 × 10⁻⁴ = **72.1 N = 16.2 lb** (7.35 kg). Tuned down to E♭4 (311.13 Hz) the same string carries 14.5 lb.

### Selected D'Addario unit weights

String typeGauges (in)Unit weight (lb/in)Plain steel (PL).009 / .010 / .011 / .0121.794 / 2.215 / 2.680 / 3.190 × 10⁻⁵Nickel-plated steel round wound (NW).024 / .032 / .042 / .0461.0857 / 1.9347 / 3.2279 / 3.8216 × 10⁻⁴Phosphor bronze round wound (PB).022 / .030 / .042 / .0530.9876 / 1.7851 / 3.4471 / 5.3270 × 10⁻⁴Clear nylon (NYL).028 / .032 / .0412.216 / 2.894 / 4.751 × 10⁻⁵Bass nickel round wound (XLB).045 / .065 / .080 / .1003.724 / 7.957 / 11.602 / 17.969 × 10⁻⁴

## Worked example

Inputs — Scale length: 25.5 in; Pitch: Choose a note; Note: E; Octave: 4; Calculate: Tension from string type and gauge; String type: Plain steel (PL); String gauge (diameter): 0.01 in.

Results — **String tension = 72.12**; Unit weight used = 0.00039555; Frequency = 329.628 Hz; Nearest note = E4; Unit-weight source = D’Addario plain steel .010″ (PL) – published unit weight 2.2150e-5 lb/in; How it feels = Typical for guitar (14–20 lb).

## Key terms

- **Unit weight (μ)**: Mass per unit length of the string, e.g. lb/in or kg/m.
- **Gauge**: String diameter, in thousandths of an inch (a “10” is 0.010″).
- **Scale length**: Vibrating length from nut to saddle.
- **Mersenne's law**: f = (1/2L)·√(T/μ) – the frequency of an ideal vibrating string.
- **Round / half-round / flat wound**: Wrap wire profiles; flat wound strings are smooth and slightly heavier.

## FAQ

**How much tension is on a guitar string?**
Most guitar strings in standard tuning carry 13–20 lb (58–90 N); a full 10–46 set adds up to roughly 100 lb (about 45 kg).

**What is the tension of a .010 high E on a 25.5″ scale?**
With D'Addario's unit weight of 0.00002215 lb/in at E4 (329.63 Hz): 0.00002215 × (2 × 25.5 × 329.63)² ÷ 386.09 ≈ 16.2 lb.

**Does a shorter scale length reduce tension?**
Yes, with the square of the length: the same .010 on a 24.75″ scale carries 15.3 lb instead of 16.2 lb.

**How much does down-tuning lower the tension?**
Each semitone down cuts tension by about 11%; a whole step (two semitones) by about 21%.

**What is a balanced-tension set?**
A set whose gauges are chosen so every string has a similar tension, giving a more even feel under the fingers.

**How do I measure string tension?**
Directly only with a tension meter; normally it is calculated from unit weight, scale length and pitch as here.

**Why do wound strings of the same gauge have different tensions?**
The core-to-wrap ratio and the wrap material (nickel, bronze, brass, stainless) change the mass per inch, so the unit weight differs.


## Sources

- [D'Addario – String Tension Specifications (unit weight chart, PDF)](https://www.daddario.com/globalassets/pdfs/accessories/tension_chart_13934.pdf)
- [Wikipedia – Mersenne's laws](https://en.wikipedia.org/wiki/Mersenne%27s_laws)
- [ISO 16:1975 Acoustics – Standard tuning frequency (A4 = 440 Hz)](https://www.iso.org/standard/3601.html)