Indian railways uses four gauges, the 1,676mm broad gauge which is wider than the 1,435mm standard gauge; the 1,000mm metre gauge; and two narrow gauge 762 mm (2 ft 6 in) and 610 mm (2 ft) . Track sections are rated for speeds ranging from 75 to 160 km/h.

The total length of track used by Indian Railways was about 111,600 km (69,300 mi) while the total route length of the network was 63,273 km (39,316 mi) on 31 March 2008. About 28% of the route-kilometre and 42% of the total track kilometre was electrified on 31 March 2008.

Broad gauge is the predominant gauge used by Indian Railways. Indian broad gauge-1,676 mm (5 ft 6 in)-is the most widely used gauge in India with 96,851 km of track length (86.8% of entire track length of all the gauges) and 51,082 km of route-kilometre (80.7% of entire route-kilometre of all the gauges) on 31 March 2008.

In some regions with less traffic, the metre gauge (1,000mm) is common, although the Unigauge project is in progress to convert all tracks to broad gauge. The metre gauge had 11,676 km of track length (10.5% of entire track length of all the gauges) and 9,442 km of route-kilometre (14.9% of entire route-kilometre of all the gauges) on 31 March 2008.

The Narrow gauges are present on a few routes, lying in hilly terrains and in some erstwhile private railways (on cost considerations), which are usually difficult to convert to broad gauge. Narrow gauges had a total of 2,749 route-kilometre on 31 March 2008. The Kalka-Shimla Railway, the Nilgiri Mountain Railway and the Darjeeling Himalayan Railway are three notable hill lines that use narrow gauge.