Conceptual Subitizer to 20

Identifies structured arrangements up to 20, shown only briefly, by seeing the parts and quickly knowing the whole. Spontaneously makes use of a top-down strategy to subitizing large quantities. Verbally labels arrangements up to 10, then up to 20, using groups.  

Children may know some familiar ones ("10 and 10 make 20" is common) early, but this level is reached when most all combinations of numbers from 1 to 10 are recognized (e.g., 7 and 9 is seen as 16).



You may see this:

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Other Examples:

  • "I saw three fives, so ten and five...15"
  • When shown two rods of 10 units, a child says “That’s 20.”
  • A child instantly recognizes “12” as a full tens-frame and 2 additional units filled, but has more difficulty with two unfilled tens-frames, such as an 8 and a 7.
  • A child "sees" 7 and 2 as 9.

Help your student become a(n) Conceptual Subitizer to 20

Short, frequent, game-like opportunities to name the number in sets up to 20 in different arrangements (such as a group of 6 next to a group of 3) only seen for 2 seconds or less help develop children's ability to quickly see a whole number by perceiving two parts. With larger numbers, structured arrangements such as five-and-tens frames are helpful. Remember for conceptual subitizing, ask them to name the total first, but then explain how they knew by naming the (preferably two) parts they saw. Encourage discussion of different "ways" to see the parts (4 and 8, 5 and 7, 6 and 6 and so forth).

Special Thanks To

Institute of Education Sciences
The research reported here was supported by the Institute of Education Sciences, U.S. Department of Education, through grant numbers R305K050157, R305A120813, R305A110188, and R305A150243. to the University of Denver. The opinions expressed are those of the authors and do not represent views of the Institute or the U.S. Department of Education.