What is the scale length of a classical guitar?

The standard scale length of a classical guitar is 650 to 660 mm (25.6 to 26 inches). That size is referred to as “full size.”
Smaller 1/4, 1/2, 3/4, and other fractional sizes are also available. However, those fractions indicate the following, rather than the proportional scale length.
 

Size	Scale Length	Appropriate Player Height
Full Size	650 mm - 660 mm (about 25.6" - 26")	150 cm or taller (about 5' or taller)
3/4	580 mm (about 22.8")	135 cm - 150 cm (about 4'6'' - 4'11")
1/2	535 mm (about 21")	115 cm - 135 cm (about 3'10'' - 4'5")
1/4	480mm (about 19")	100 cm - 115 cm (about 3'3'' - 3'9")