The current 24-hour layout of Circuit de la Sarthe is 13.626 km long. That distance describes the modern endurance-race configuration used for the 24 Hours of Le Mans, rather than the shorter Bugatti Circuit at the same venue.
Circuit de la Sarthe is unusually long because it links permanent racing infrastructure with public roads around Le Mans and Mulsanne. The route includes the Dunlop section, Tertre Rouge, the Mulsanne Straight, Mulsanne Corner, Indianapolis, Arnage and the Porsche Curves before returning to the start-finish area.
The 13.626 km figure applies to the configuration in use from 2018 onward. Earlier layouts had slightly different measurements: the 2007–2017 version was 13.629 km, while the 2002–2006 version measured 13.650 km. These small changes reflect safety and corner-profile revisions.
The 16.340 km option is historically real, but it belongs to a 1929–1931 layout. That is why it can look plausible in older references while still being incorrect for the current circuit.