About the World Nuclear Weapons Stockpile Report
A quarter century after the end of the Cold War, the world’s combined stockpiles of nuclear weapons remain at unacceptably high levels.
Hans Kristensen  and Robert Norris  of the Federation of American Scientists  are the leading experts in estimating the size of global nuclear weapons inventories. The table is a compilation of their estimates and analyses, with links to their full reports. These reports are published in The Bulletin of the Atomic Scientists  and discussed further at the FAS Strategic Security Blog .
As the authors of these estimates note, the above numbers may not add up due to rounding and uncertainty about the operational statuses and size of the total inventories. For a full analysis of how the authors arrived at their estimates, please view the provided links for the complete reports.
Updated March 2, 2016.