String Tension Calculator

Set up a comparison

Choose a string set and tuning, then enter the vibrating scale length in inches. The rows run from the highest string downward. Changing a gauge or pitch recalculates the complete setup; No string removes that position from the total.

Select New guitar to compare a second configuration. When moving between guitar and bass sets, the calculator changes the default scale and tuning to match the instrument. You can then adjust either dimension. Saved setups stay in this browser and are recalculated when reopened.

What the calculation measures

The result is a pulling force. Pounds-force (lbf), newtons (N), and kilograms-force (kgf) describe that force; pounds per inch instead describe the unit weight used as an input. One lbf equals approximately 4.44822 N or 0.45359237 kgf.

For inches and unit weight in lb/in, the formula is T = UW × (2 × L × f)² ÷ 386.4. Here L is the scale length and f is the frequency in hertz. Holding everything else constant, a longer scale or higher pitch increases tension quadratically.

Reference strings and accuracy

This tool uses published D’Addario unit weights for plain steel, nickel-wound guitar strings, and nickel-wound bass strings. Set names select a gauge combination; they do not load a separate weight table for every string manufacturer.

Intermediate gauges use linear interpolation. A gauge outside the reference table uses an area-based estimate, which is less dependable for wound construction. Nylon, phosphor bronze, flatwound, and tapered strings need their own mass data and are not modeled here.

As a reference check, a .010 plain string tuned to E4 on a 25.5-inch scale produces about 16.2 lbf. A .046 nickel-wound guitar string at E2 on that scale is approximately 17.5 lbf. Matching the outside diameter alone does not guarantee another brand will produce those figures.

Multiscale lengths and tuning changes

In multiscale mode, enter the highest and lowest string lengths. The intermediate positions are spaced linearly between those endpoints. That is an approximation to a particular instrument: use its measured string lengths when you need a precise comparison.

Lowering the same string by one whole tone reduces its calculated force to about 79.4% of the previous value. This explains why a familiar set feels looser in a lower tuning. The thickness needed to restore the old feel also depends on its construction.

Tension does not tell the whole playing story

Equal forces do not guarantee equal bending resistance. String construction, action, and the instrument’s hardware also influence what you feel. Compare a proposed setup with one you already enjoy rather than treating a universal green or red range as a target.

A different set may require changes to the setup, particularly on a floating tremolo. The calculator estimates string force; it does not assess neck condition, nut fit, or how far a truss rod should turn.