核武器当量是指核武器爆炸后释放出的能量，通常用释放出相同能量的*****的吨位来衡量。常见的单位有千吨（kt）和百万吨（Mt），有时也用太焦耳（TeraJoules）。因为测量TNT爆炸产生的能量具有一定主观性，加之试验误差，精确测定很困难（特别是在核武器研发初期）。因此，一千吨TNT爆炸的能量约定俗成的定为10大卡，相当于4.184太焦耳。

当量-重量比是指核武器的当量与其重量的比值。对于聚变武器（热核武器），当量-重量比的理论极限是每吨位炸弹6百万吨TNT，相当于25太焦耳/千克。1960年代曾报道过当量在5.2百万吨／吨，甚至更高的单弹头核武器。但从那时起，为了增加打击效率，多弹头核武器受到青睐。因此，核武器开始小型化，现代单弹头核武器的当量-重量比开始走下坡路。

The explosive yield of a nuclear weapon is the amount of energy released when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produce the same energy discharge), either in kilotons (kt—thousands of tons of TNT), in megatons (Mt—millions of tons of TNT), or sometimes in terajoules (TJ). An explosive yield of one terajoule is 0.239 kt of TNT. Because the accuracy of any measurement of the energy released by TNT has always been problematic, the conventional definition accepted since the dawn of the Atomic Age is that one kiloton of TNT is simply to be 10 calories equivalent, which only approximately equal to the energy yield of 1,000 tons of TNT.