The most commonly used gauge today is the standard gauge of 1,435 mm – in early 19th century England this was 4 feet 8.5 inches. This gauge was first used in England in 1825 by the legendary railway pioneer George Stephenson.

The most used railway gauge in the world is the Standard Gauge, which measures 1,435 mm (4 ft 8½ in) between the inner edges of the rails. Often called the "Stephenson Gauge" after the British engineer George Stephenson, it accounts for approximately 60% of the world's railway lines. It is the international standard for North America, most of Western Europe, China, and almost all of the world's high-speed rail networks, including the Japanese Shinkansen and the French TGV. The remaining 40% of the world's tracks use either "Broad Gauge" (common in Russia, India, and parts of Australia and Spain) or "Narrow Gauge" (prevalent in Southeast Asia, Africa, and Japan's older regional lines). The global dominance of the 1,435 mm gauge is largely a legacy of British railway engineering influence during the 19th century, which allowed for the eventual interconnection of national rail systems across continents, facilitating the seamless movement of freight and passengers across international borders.