The alimentary canal (or the digestive tract) covers the distance from the mouth to the anus.
(From lifespa.com)
However, the distance varies according to body type.
The intestinal distance in an ectomorph ("little fat or muscle") can be as little as 6 m and as much as 9 m for endomorphs ("much fat and muscle").
Here is a summary of the distances I found.
#color(white)(m)bb"Segment" color(white)(mm) bb"Length/m" color(white)(m)bb"Subsegment"color(white)(cm) bb"Length/cm"#
#color(white)(ll)"Mouth to"#
#color(white)(ll)"duodenum" color(white)(mmml)0.5 color(white)(mmmmmmmmmmmm)50#
#color(white)(ll)"Small"#
#color(white)(ll)"Intestine"color(white)(mmmml)6.3color(white)(mmll)"Duodenum"color(white)(mmmll)30#
#color(white)(mmmmmmmmmmmmml)"Jejunum"color(white)(mmmml) 250#
#color(white)(mmmmmmmmmmmmmll)"Ileum"color(white)(mmmmmll)350#
#color(white)(ll)"Large"#
#color(white)(ll)"Intestine"color(white)(mmmml) 1.8color(white)(mmll) "Cecum" color(white)(mmmmmmll) 5#
#color(white)(mmmmmmmmmmmmmll)"Ascending" color(white)(mmmml)10#
#color(white)(mmmmmmmmmmmmmll)"Transverse" color(white)(mmmm) 65#
#color(white)(mmmmmmmmmmmmmll) "Descending" color(white)(mmmll) 10#
#color(white)(mmmmmmmmmmmmmll)"Sigmoid"color(white)(mmmmml) 65#
#color(white)(mmmmmmmmmmmmmll)"Rectum"color(white)(mmmmml) 20#
#color(white)(mmmmmmmmmmmmmll)"Anus" color(white)(mmmmmmml) 5#
#color(white)(mmm)"TOTAL ="color(white)(m) 8.6#
