There is no single Camino, so the answer depends on where you start; the distances above are the ones most Americans mean. The Francés figure covers roughly 33 conventional stages averaging 24 km (15 mi): the Pyrenees on day one, the Navarre and Rioja vineyards, the flat meseta between Burgos and León, the mountains of El Bierzo, and the Galician hills. Walkers who add rest days or shorten stages to about 20 km land at the 40-day end; fit walkers who keep to 25 to 30 km reach Santiago in about 30.
Sarria to Santiago is the stretch the Galician government maps in six stages: Sarria to Portomarín 22 km, Portomarín to Palas de Rei 25.1 km, Palas de Rei to Melide 14.6 km, Melide to Arzúa 14.5 km, Arzúa to O Pedrouzo (Arca) 18.4 km, and O Pedrouzo to Santiago 20.2 km, a total of 114.8 km (71 mi). Most people walk it in five or six days; the existing page on how difficult Sarria to Santiago is covers the terrain.
From Porto there are two ways, the central through Barcelos and Ponte de Lima and the coastal along the Atlantic, both roughly 240 km and 10 to 12 days, meeting at Redondela; from Tui, the first town in Spain, the central way is 118 km, which the Galician government measures at 118.8 km from the border. Cyclists must cover 200 km, so León or Porto are the usual bicycle starts. Whatever the route, the Pilgrim's Office counts only continuous kilometers into Santiago, so a bus-assisted section does not shorten the requirement.