An estimate for the number of cells in an adult human being is ~37.2 trillion [1]. Let's be conservative and round that up to 40, and then assume that everyone

An estimate for the number of cells in an adult human being is ~37.2 trillion [1]. Let's be conservative and round that up to 40, and then assume that everyone on earth is an adult, too. There are currently 7.49 billion people in the world [2]. Let's be conservative again and round that up to 8. Multiplying these numbers gives us 3.2x10^23 cells. The IPv6 Global Unicast address space (2000::/3) is 125 bits wide, for 2^125 = 4.3x10^37 combinations. This gives us 1.33x10^14 addresses per cell. Ofcourse, thinking about IPv6 in terms of number of addresses is wrong, because you should be thinking in terms of number of networks (/64). That gives us 2^(125-64) = 2.3x10^18 networks, or 0.000007 networks per cell, which is 268054250 networks per person. I think we're okay. [1] http://www.smithsonianmag.com/smart-news/there-are-372-trillion-cells-in-your-body-4941473/ http://www.smithsonianmag.com/smart-news/there-are-372-trill... [2] http://www.worldometers.info/world-population/ http://www.worldometers.info/world-population/ EDIT: Fixed formatting.