the pmcolt equation
N = R_a * P_x * F_j * F_dv * N_k * 4A * B_s * F_f * Q
R_a = number of Reptilian alien overlords on Earth at any given time
P_x = the population of Planet X
F_j = fraction of the population that are Jedi
F_dv = fraction of Jedi who become Darth Vader
N_k = nuke 'em from orbit
4A = average cattle mutilations per year
B_s = probability that the moon landing was faked
F_f = fudge factor
Q = Jean Luc Picard's archrival
I'm not sure what it calculates, but I feel I'm on to something important.
The Drake Equation needs to be taken for what it is: a thought experiment. It's a Fermi problem to help us think about what the answer is (the number of communicating ET civilizations in the galaxy), what factors influence that number (the terms of the equation), our basic assumptions (that life depends on stars, on planet formation, etc.), and how certain we are of our knowledge (not even enough to make a zero-order approximation).
It's a mechanism to tie together all the bits of information that we think are important in determining how common intelligent life is. It's something to be used to guide speculative SETI scientists looking to pin down some of these factors. It's something to dust off and play with for our own amusement. Which is exactly what we're doing, so in that respect. Frank Drake was successful.
(Also, the equation is naturally metric. What advanced civilization would still be using the standard system?)