String Tension Calculator
Calculate string tension from the published formulas and tables for the craft.
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What this tool does
Calculate string tension from the published formulas and tables for the craft. Unit weights are D'Addario's published chart values for its plain-steel (PL) and nickel-wound (NW) singles, labelled per string; use the override with the chart value for any string not listed. Tension assumes the entered scale length and pitch exactly.
How to use the String Tension Calculator
- Enter or select scale length (inches).
- Enter or select note frequency (hz).
- Enter or select string (d'addario chart unit weight).
- Enter or select unit weight override (lb/in, 0 = use chart value).
- Read the calculated result; change any measurement to compare alternatives.
Formula
D'Addario tension formula: tension (lb) = unit weight (lb/in) × (2 × scale length × frequency)² ÷ 386.09
- scale
- Scale length (inches)
- frequency
- Note frequency (Hz)
- string
- String (D'Addario chart unit weight)
- uwOverride
- Unit weight override (lb/in, 0 = use chart value)
Unit weights are D'Addario's published chart values for its plain-steel (PL) and nickel-wound (NW) singles, labelled per string; use the override with the chart value for any string not listed. Tension assumes the entered scale length and pitch exactly.
Worked example
For string tension calculator, the following measurements illustrate the exact method: Scale length (inches): 25.5; Note frequency (Hz): 329.63; String (D'Addario chart unit weight): pl010; Unit weight override (lb/in, 0 = use chart value): 0.
Inputs
- Scale length (inches)25.5
- Note frequency (Hz)329.63
- String (D'Addario chart unit weight)PL010 plain steel .010
- Unit weight override (lb/in, 0 = use chart value)0
Result
- String tension (lb)16.21
- String tension (kg)7.35
- String tension (newtons)72.12
- Unit weight used (lb/in)0
Results explained
- String tension (lb)
- String tension (lb) from the formula above. Unit weights are D'Addario's published chart values for its plain-steel (PL) and nickel-wound (NW) singles, labelled per string; use the override with the chart value for any string not listed. Tension assumes the entered scale length and pitch exactly.
- String tension (kg)
- String tension (kg) from the formula above. Unit weights are D'Addario's published chart values for its plain-steel (PL) and nickel-wound (NW) singles, labelled per string; use the override with the chart value for any string not listed. Tension assumes the entered scale length and pitch exactly.
- String tension (newtons)
- String tension (newtons) from the formula above. Unit weights are D'Addario's published chart values for its plain-steel (PL) and nickel-wound (NW) singles, labelled per string; use the override with the chart value for any string not listed. Tension assumes the entered scale length and pitch exactly.
- Unit weight used (lb/in)
- Unit weight used (lb/in) from the formula above. Unit weights are D'Addario's published chart values for its plain-steel (PL) and nickel-wound (NW) singles, labelled per string; use the override with the chart value for any string not listed. Tension assumes the entered scale length and pitch exactly.
Frequently asked questions
With D'Addario's formula: tension = unit weight × (2 × scale length × frequency)² ÷ 386.09 (gravitational constant in in/s²). A .010 plain string at E4 (329.63 Hz) on a 25.5 in scale with chart unit weight 0.00002215 lb/in gives about 16.2 lb.
They are the values printed in D'Addario's published string tension chart for its PL plain-steel and NW nickel-wound single strings, shown in each option's label. Strings from other makers differ slightly; for an unlisted string, type its chart unit weight into the override field.
Tension grows with the square of both frequency and scale length. One semitone up (×1.0595 frequency) adds about 12% tension; the same string set on a 27 in baritone scale carries roughly 12% more tension than on a 25.5 in scale at the same pitch.
Add the six per-string results. A typical .010–.046 set on a 25.5 in scale at standard tuning totals around 100–110 lb; a .009 set is nearer 85 lb, and 12-string sets can exceed 200 lb, which is why neck relief changes with gauge.
Yes: higher tension feels stiffer, bends harder and sounds tighter and brighter with better tuning stability; lower tension (shorter scale, lighter gauge or down-tuning) feels looser and warmer but can fret-buzz and go sharp when picked hard. Builders use tension to match a gauge set to a tuning.