The Stockholm International Peace Research Institute (SIPRI) has recently published its 2011 Yearbook, which estimates the number of nuclear weapons in the world. Only four countries have deployed nuclear warheads, that is, warheads placed on missiles or on bases with operational forces. Of these, the US has 2,150 and Russia 2,427. Under the terms of the START agreement between the US and Russia, ratified in 2010, each country is required to reduce the number of deployed strategic warheads to1,550 by the year 2017. The other two countries with deployed nuclear weapons are the UK with 160 and France with 290. SIPRI estimates that about 2,000 of these 5,027 are kept on high operational alert, ready to be fired within moments.
US 6,350; Russia 8,570; UK 65; France 10; China 240; India 80-100; Pakistan 90-110; Israel 80.
This information is from David Krieger, US Nuclear Age Peace Foundation, 09.06.11