The Acolhua, like other mesoamerican groups, used base 20.

Their unit of measurement was the Tlalcuahitl, T, which is equivalent to to 2.5m or about 8feet.

In codices Vergara and Santa María Asunción, in linear measurements one line represents 1,

5 lines with a line on top represent 5 and a dot represents 20.

In the following figure the lengths of the sides, in clockwise order starting from the bottom are  20,20,18,20.

As to fractions, the arrow represents  1/2, the heart has been interpreted as  2/5 or as 1/3

and the hand as 3/5 or as 2/3.

In the following figure, starting at the lower left corner and moving in clockwise order the sides are

15, 28, 15, 28+heart and  39, 22, 5, 3+arrow, 25+hand, 4, 5, 22.
 

For areas the  Acolhua used a proto-positional  ad hoc notation in which numbers that appeared in the center or bottom were multiplied by 20 and those in the tab were not.

The square unit was T squared.