Brains aren't built for FLOPS. In fact, compared to computers, we suck at them. I can't do a floating point add of the decimal representations of 32-bit (single-precision) numbers in a second or less. I probably couldn't work with the binary representations any faster. So, in terms of FLOPS, my guess is that a bound based on adds would be somewhere around .001 to .1 FLOPS, and if we include multiplies, then maybe less than $10^{-3}$ FLOPS.
The fairest comparison is to measure the brain's computing power in instructions per second, or IPS, which would be comparable to integer operations for a CPU. Estimates for the computing capacity of a computer vary (see Ars Technica quoting an article in Science, insideHPC quoting a researcher, a UAlberta professor of psychology doing a back-of-the-envelope calculation, and an Oracle-sponsored project). The range seems to be $10^{11}$ to $10^{18}$ IPS, omitting prefactors from the scientific notation.
As for the storage capacity of the brain, those same articles quote a range of around $10^{8}$ to $10^{15}$ bits of storage, depending on estimation method. The range of estimates for both processing power and storage tend to try to account for the fact that the brain and computer hardware are designed for fundamentally different sets of tasks. Regardless, for the quoted processing power and storage numbers, the human brain is the more efficient of the two "computers" on a power basis, requiring roughly 2000ish calories per day of sustenance (plus the right micronutrients), whereas a computer typically requires a power supply in tens to hundreds of watts.