How wide are railroad tracks? The US standard railroad gauge is 4 feet, 8.5 inches (Gauge means width between the two rails). The U.S. federal safety standards allow the standard gauge to vary from 4 ft 8 in (1,420 mm) to 4 ft 9 1/2 in (1,460 mm) for operation up to 60 mph (97 km/h).

The "standard gauge" for railway tracks used across approximately 60% of the world's railroads is 1,435 mm (or 4 feet 8.5 inches). This specific width was popularized by George Stephenson in Britain and was later adopted as the international standard to allow for interoperability between different rail networks. While some countries use "narrow gauge" for mountainous terrain or "broad gauge" (such as the 1,676 mm gauge in India and Argentina) for increased stability, the 1,435 mm gauge remains the most common for high-speed rail and major international corridors. Interestingly, a popular legend suggests this width can be traced back to the wheel ruts created by Roman chariots, though most historians credit the standard to the practical dimensions of early coal wagons used in northern England.