The relation describing the physics in a string is given by the following equation

- f = frequency - in Hz or cycles/second
- L = string length (between nut and bridge) - in meters
- T = Tension (Force) on the string - in Newtons
- P = Unit Weight of the string - in Kg/m

Reworking this equation to get the Tension on the string:

It is interesting to note that the Force or Tension on the string is the accumulation (multiplications)
of all the factors in the relation.

This is the fundamental equation describing the tension on a string. The confusion arises when
adapting this equation for different units. Tension is often mistakenly given in Kg or Pound. This
should be kgf or kg_{F} (Kilogram force) and lb_{f} (Pound force).
To convert Newtons into Kilogram force, use the following unit conversion:

Hence the fundamental equation can be written as

- f = frequency - in Hz or cycles/second
- L = string length (between nut and bridge) - in meters
- T = Tension (Force) on the string - in kg
_{F} (Kilogram force)
- P = Unit Weight of the string - in Kg/m

To convert Newtons into Pound force, use the unit conversion

Therefore the fundamental equation can be rewritten as

- f = frequency - in Hz or cycles/second
- L = string length (between nut and bridge) - in meters
- T = Tension (Force) on the string - in lb
_{f} (Pound force)
- P = Unit Weight of the string - in Kg/m