A standard full-size school bus in the United States is typically about 40 feet long.
That figure describes the large buses commonly used for regular school routes, especially Type C conventional buses and Type D transit-style buses. Exact dimensions vary by manufacturer, body configuration, wheelbase, and seating layout, so 40 feet is a useful typical figure rather than an absolute limit. Smaller Type A buses can be far shorter, while some full-size models approach or exceed that length.
School-bus size is often discussed alongside vehicle classification. Type C buses have a separate hood and engine compartment, while Type D buses place the driver ahead of the front axle and use a flat-front design. Both can be built as large-capacity buses near the 40-foot range.
The 40-foot answer should not be confused with the length of every school bus. Activity buses, special-needs buses, and vehicles based on vans may be much shorter. Nor is 50 feet the standard U.S. school-bus length; that figure is closer to an unusually long vehicle than the common full-size model.