The most common gauge is 'standard gauge', or 'Stephenson Gauge' which is 1435 mm (originally 4 ft 8½ inches). Standard Gauge is used by 60% of the world's railways
- 1435 mm Standard Gauge is used on most of Europe, North America, China and parts of South America, Africa and Australia.
- 1520 mm is used in Russia and countries which used to be part of the Russian Empire.
- 1600 mm is used in Ireland and parts of South America and Australia.
- 1668 mm is used in Spain and Portugal.
- 1676 mm is used in India and Pakistan.
- 1000 mm is used for some branch lines and trams in Europe, and in parts of South America and Australia.
- 1067 mm (3 ft 6 in) is used in Japan and parts of South America, Africa and Australia.
Plus many other gauges used locally for short sections of railway.
New High Speed lines are built to Standard Gauge, even in countries that do not use Standard Gauge (Japan, Spain) because it is cheaper to use existing designs for the trains.
