Fuel is stored in three tanks; the left main, the centre, and the right main. There is also a surge tank outboard of each main tank, the function of these being to temporarily hold fuel that flows out from the main tanks due to aircraft turns, or to thermal expansion, or overfill.

The Boeing 777 typically features three primary fuel tanks: a massive center wing tank and two wing-integrated main tanks (one in the left wing and one in the right). For the standard 777-200 or 777-300, this configuration provides a total fuel capacity of approximately 117,340 liters (31,000 U.S. gallons). However, the ultra-long-haul variants like the 777-200LR and 777-300ER are designed to carry significantly more fuel to reach distant continents. These variants often include the option for up to three additional auxiliary fuel tanks located in the rear cargo compartment. These "aux" tanks increase the range but reduce cargo space. The fuel system is highly automated, using a series of pumps and cross-feed valves to ensure the weight remains balanced across the aircraft's center of gravity throughout the flight. During pre-flight, the "Fueler" and the pilot-in-command coordinate the exact tonnage needed, accounting for the route, wind conditions, and mandatory emergency reserves.