Measuring using Calories:
Gasoline produces about 7594000 calories per liter
1 calorie = 4.184 joules
4.184 x 7594000 = 31773296 j/L, or 3.17e+7 j/L
For joules per gallon:
1 gal = 3.78541 L
31773296 j/L x 3.78541 L/Gal = 120274952.411 j/Gal, or 1.207e+8 j/Gal
An average tanker can hold approximately 5,500 to 11,600 gallons of gasoline.
Low-End:
1.207e+8 x 5500 gallons = 6.6385e+11 J, Multi-City Block level
High-End:
1.207e+8 x 11600 gallons = 1.40012e+12 J, Multi-City Block level+
Measuring using Energy Density of Gasoline:
Energy density of gasoline = 46.4 mj/kg of Gasoline
The density of gasoline = 719.7 kg/m^3
Volume of a tanker = 5500 gal to 11600 gal, or 20.81976 m^3 to 43.910777 m^3
Low-End:
719.7 kg/m^3 x 20.81976 m^3 = 14983.981272 kg
14983.981272 kg x 46.4 MJ = 695256.731021, 166.17033939 tons of tnt, Multi-City Block level
High-End:
719.7 kg/m^3 x 43.910777 m^3 = 31602.5862069 kg
31602.5862069 kg x 46.4 MJ = 1466360, 350.47 tons of tnt, Multi-City Block level
Summary:
Energy via Calories Low-End = 158.67 Tons of tnt, Multi-City Block level
Energy via Calories High-End = 334.6 Tons of tnt, Multi-City Block level+
Energy via Gasoline Density Low-End = 166.67 Tons of tnt, Multi-City Block level
Energy via Calories Low-End = 350.47 Tons of tnt, Multi-City Block level+