  We have developed a method to determine the transient surface density and
transient rate for any given survey, using Monte-Carlo simulations. This method
allows us to determine the transient rate as a function of both the flux and
the duration of the transients in the whole flux-duration plane rather than one
or a few points as currently available methods do. It is applicable to every
survey strategy that is monitoring the same part of the sky, regardless the
instrument or wavelength of the survey, or the target sources. We have
simulated both top-hat and Fast Rise Exponential Decay light curves,
highlighting how the shape of the light curve might affect the detectability of
transients. Another application for this method is to estimate the number of
transients of a given kind that are expected to be detected by a survey,
provided that their rate is known.
