ENORMOUS ENERGY DENSITY. “The reaction of 1 kg of antimatter with 1 kg of matter would produce 1.8×10(17) J (180 petajoules) of energy (by the mass–energy equivalence formula, E=mc2), or the rough equivalent of 43 megatons of TNT – slightly less than the yield of the 27,000 kg Tsar Bomba, the largest thermonuclear weapon ever detonated.”
https://en.m.wikipedia.org/wiki/Antimatter