The takeoff speed of a Boeing 747 can vary depending on factors such as aircraft weight, runway length, temperature, altitude, and other conditions. However, as a general estimate, a fully loaded Boeing 747 typically requires a takeoff speed of around 150 to 180 knots (170 to 210 miles per hour or 280 to 340 kilometers per hour).
It's important to note that this is a rough estimate, and the actual takeoff speed may vary depending on the specific circumstances and configurations of the aircraft during a given takeoff. Pilots rely on detailed performance charts, calculations, and aircraft instrumentation to determine the precise takeoff speeds for each situation.