Convert kilojoule to kilotonne TNT

The calorie of food labels is really the kilocalorie: 1 kcal = 1,000 cal = 4.1868 kJ, the heat that warms a kilogram of water by one degree. Nutrition labels in the EU must give both kJ and kcal, the US gives 'Calories' with a capital C meaning kcal, and the adult reference intake is 2,000 kcal, about 8,400 kJ. A slice of bread is around 80 kcal, an hour's brisk walk burns about 300.

The tonne of TNT is defined as 4.184 GJ, about the energy released by detonating a tonne of the explosive, and is the unit of nuclear yields and of large explosions and impacts. The Hiroshima bomb was about 15 kt, the largest weapon ever tested (Tsar Bomba, 1961) 50 Mt, the 2020 Beirut explosion roughly 0.5 kt, and the Chicxulub impact that ended the dinosaurs on the order of 100 million Mt.