The maximum length for a school bus allowed on US highways is 45 feet.
In the United States and Canada, school-bus bodies are generally limited to 102 inches in width and 45 feet in length. The limit applies to the standardized North American school-bus market, where large buses must balance passenger capacity with maneuverability on school routes, residential streets, and loading areas.
A 45-foot maximum does not mean every full-size school bus reaches that length. Many conventional and transit-style buses are shorter, depending on the manufacturer, district specifications, wheelbase, and seating plan. State and local rules can also impose additional requirements, so a particular route or jurisdiction may use a lower practical limit.
The length rule is easy to confuse with seating capacity. A longer body can accommodate more rows, but emergency exits, wheelchair equipment, aisle dimensions, fuel systems, and operator preferences all affect the final layout. School buses also differ from ordinary coaches in their stop equipment, warning lights, compartmentalized seating, and purpose-built construction.