Finding the length of a pendulum

[Bugsy23]

Is there more than one way to find the length of a pendulum undergoing lightly damped harmonic motion? The equation I have is

l=(T/2pi)^2*g

Is there an alternative equation for calculating length, which also takes into account the oscillator's mass?

 

[cjl]

The oscillator's mass is not actually relevant for a situation in which damping is negligible. If damping is non-negligible, then you would also need to know details about the damping to determine the length.