How much sea ice are we losing? Search for a location (US state, country, etc.) to see
I took sea ice extent data from the NOAA. I averaged that data from January 1981 to December 2000 to come up with the reference period. I then averaged the values over the years specified (2006, 2011, 2016) and the difference between those values is the sea ice lost. I took areas for locations from wikipedia. Sea ice lost divided by the area of a location gives you the number that you see in the results.
Note that the image used in the tools page for this tool is By Patrick Kelley [CC BY 2.0], via Wikimedia Commons