【How-to】How wide is 35mm - Howto.org

Counting the leader, a 36 exposure roll of film is about 63 inches in length. With avoirdupois translated into metric, that 63 inches becomes 1600 millimeters per roll. (i.e. 63 inches x 25.4mm per inch). This 1600mm length times the 35mm width becomes 56,000 square millimeters of film per roll, total.