Width of broad-gauge in railways

Width of broad-gauge in railways is 5'6".

Broad gauge means the rails are farther apart than the 1435mm used in "Standard gauge" railways. There are a number of different broad gauges in use. For example:

1520 mm used in Russia and countries which used to be part of the Russian Empire.

1600 mm used in Ireland

1668 mm used in Spain and Portugal.

1676 mm used in India and Pakistan.