Nuclear weapons are typically measured in tons of TNT. The large explosive power of these weapons means that nuclear weapons are typically measured in Kilotons or Megatons. 1000 Kilotons is 1 Megaton. One of the smallest nuclear devices was the W54, with a possible explosive power of 10 tons. The largest, the Tsar Bomba, was ~50 Megatons, with a possible explosive yield of 100 megatons.