The takeoff speed of a Boeing 747 can vary depending on several factors, including the weight of the aircraft, temperature, altitude, and runway length. Generally, the takeoff speed for a fully loaded Boeing 747 is around 160-180 knots (184-207 mph or 296-333 km/h). However, it's important to note that this is just an approximate range and can vary.

The weight of the aircraft plays a significant role in determining the takeoff speed. A fully loaded Boeing 747 can weigh around 900,000 pounds (408,233 kg) or more. The heavier the aircraft, the higher the speed required for takeoff. For example, a lightly loaded 747 might require a lower speed, while a fully loaded one will need a higher speed to generate enough lift to get off the ground.

Temperature and altitude also affect the takeoff speed. Higher temperatures and altitudes reduce the air density, which means the aircraft needs a higher speed to generate sufficient lift. For instance, at higher altitudes, such as airports located in mountainous regions, the takeoff speed may be higher compared to airports at lower altitudes.

Runway length is another crucial factor. Longer runways allow the aircraft to accelerate to a higher speed before taking off, which can reduce the required takeoff speed. Conversely, shorter runways may necessitate a higher takeoff speed.

It's worth mentioning that the takeoff speed is not a fixed value but rather a range. The exact speed for a specific takeoff can be calculated using performance charts provided by the aircraft manufacturer. These charts take into account various factors, including weight, temperature, altitude, and runway length, to determine the precise takeoff speed required for a given situation.

Sources:

1. "Boeing 747-400 Airplane Characteristics for Airport Planning" - Boeing Commercial Airplanes.

https://www.boeing.com/resources/boeingdotcom/company/about_bca/pdf/747_400x.pdf

2. "How fast does a 747 need to go to take off?" - Quora.

https://www.quora.com/How-fast-does-a-747-need-to-go-to-take-off