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String Tension Calculator

Work out string tension instantly with clear inputs, formula shown and shareable results.

About String Tension Calculator

The standard string tension formula is T = unit weight x (2 x scale length x frequency)^2 / 386.4, where 386.4 is gravitational acceleration in inches per second squared. Because tension rises with the square of both length and pitch, moving from a 25.5 inch to a 27 inch baritone scale at the same pitch adds over ten percent tension.

Formula

String tension

T (lb) = unit weight x (2 x L x f)^2 / 386.4

Worked example

With the default values below, String Tension Calculator returns String tension of 5.701. Change any input above and every figure here is recalculated in your browser.

Inputs used

Scale lengthminimum 1 in
25.5 in
String unit weightminimum 0 lb/in
0.00007 lb/in
Pitch frequencyminimum 1 Hz
110 Hz

Results

String tension
5.701 lb
Tension in kilograms force
2.586 kgf
Tension in newtons
25.36 N
Rough total for six similar strings
34.21 lb

Step by step

  1. 1Values used
  2. 2String tension
  3. 3String tension= 5.701 lb
  4. 4Tension in kilograms force= 2.586 kgf
  5. 5Tension in newtons= 25.36 N
  6. 6Rough total for six similar strings= 34.21 lb

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or fees or charges into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the String Tension figure worked out?

T (lb) = unit weight x (2 x L x f)^2 / 386.4. The standard string tension formula is T = unit weight x (2 x scale length x frequency)^2 / 386.4, where 386.4 is gravitational acceleration in inches per second squared.

Why does this matter?

Because tension rises with the square of both length and pitch, moving from a 25.5 inch to a 27 inch baritone scale at the same pitch adds over ten percent tension.

What do I need to enter?

Enter scale length, string unit weight, pitch frequency. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

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