When Googling for the answer as to how fast the human brain works, you'll get a range of values. As it happens the first response agreed:
Furthermore, there is no real consensus regarding the computational power of the human brain. Some estimates suggest that it is capable of 1017 FLOPS, or a 100 petaflops.
The brain doesn’t function like a digital computer, and no one has completely modeled a linked cluster of neurons, so estimates of computing power are, at the moment, garbage.
Even the rather rigidly wired visual cortex hasn’t been modeled. The temporal lobes — the ones most distinctively large in humans, have not been analyzed in any meaningful way.