Russia and US have most number of nuclear weapons available in the world

Only Nine countries are Nuclear-capable in the world they are Russia, US, Uk, China, France, Israel, Pakistan, India, North Korea. But among these nine only eight (except north korea) are believed by experts to have weapons mature and developed enough to be readily incorporated into the arsenals of their armed forces.

Russia and US are believed to have most nuclear weapons today. 4,300 in Russia and United States, with 4,000.
Total there are around 15,000 nuclear weapons in the world among them 9,400 are in military arsenals. The remaining weapons are retired and awaiting dismantlement. Nearly 4,000 are operationally available, and 1,800 are ready for use on short notice.