Many biophysical studies involve diffusing particle in a potential field, especially in a harmonic potential field. Optical tweezers, magnetic tweezers and tethered particle motion (TPM) are some examples for such experiments. In order to extract dynamical properties from these experiments, there is a need to accurately calibrate the setup.

We developed a method, based on the known solution of Smoluchowski's equation, for finding all of the relevant parameters (i.e. the particle's diffusion coefficient and the spring constant of the harmonic potential) without pre-calibrating the setup. We used computer simulation together with TPM experiments to test our method, and we found that this method has advantage over the typical methods.