Sofa width
Each arm
People
Shoulders
Narrower (about 42 cm)
Average (about 47 cm)
Broader (about 55 cm)
Try a 2-seater (160 cm)
Try a 3-seater (220 cm)
Try a long one (260 cm)
between the arms
per person
people at about 60 cm each
Front view, zoomed to fit the sofa. Bodies are simplified: shoulders and hips only. The 60 cm line is a rule of thumb, not a law.