Currently we use Ghz to measure our computer's power.My computer is the good old P4 with a 2.4Ghz processor.
Lets see how many Ghz a human brain is?
The retina is a nerve tissue in the back of the eyeball which detects lights and sends images to the brain. A human retina has a size of about a centimeter square is half a millimeter thick and is made up of 100 million neurons. Scientists say that the retina sends to the brain, particular patches of images indicating light intensity differences which are transported via the optic nerve, a million-fiber cable which reaches deep into the brain.
Overall, the retina seems to process about ten one-million-point images per second.
Because the 1,500 cubic centimeter human brain is about 100,000 times as large as the retina, by simple calculation, we can estimate the processing power of a average brain to be about 100 million MIPS (Million computer Instructions Per Second ). In case you're wondering how much speed that is, let us give you an idea.
According to above example in which we took retina as a unit,our brain works at 1680 Ghz of Pentium computer.
Fast isn't it? 
