TDSB Mathematics for Families & Caregivers

Subitizing

Overview

When students see dots on a die, some students will count the dots, but others with more experience recognizing quantity will subitize. Subitizing is the ability to recognize the number of objects at a glance without having to count all the objects – for example, knowing that a collection holds 5 beads without having to count them.

Subitizing is an essential strategy that is fundamental to the development of strong number sense. Subitizing can help lay the foundation for work with place value, addition and subtraction, and estimation. For example, students looking at the number 32 can visualize 3 ten frames and 2 more; students can see a representation of 7 as 3 + 4.

There are two types of subitizing:

Perceptual subitizing happens when you look at a group of objects and know how many objects there are without thinking. This often happens when we look at groups with five objects or less.
Conceptual subitizing happens with larger sets of numbers when we decompose the set into smaller sets that we can instantly recognize and add together. We often shift to conceptual subitizing when the number of objects in the group is greater than 5. We are also able to perceptually subitize groups of more than 5 when the items are organized in a familiar way (e.g., the 6 pips on a die). In the beginning, you might see the 6 pips as two columns of three added together to make six until it becomes more familiar and you eventually memorize the quantity as six.

While students are learning the counting principles, these principles, such as subitizing, are important foundational skills that must be consolidated into a strong understanding. You will find that many of the counting principles are interconnected. Once students have a solid understanding of the counting principles, many of them will become key ideas that support students as they develop addition/subtraction strategies for learning mathematics.

Supporting Students with Subitizing

To support students learning to subitize, provide many opportunities to practice subitizing small numbers (1-5). Once students have mastered 1-5, you can begin to introduce larger numbers using familiar patterns and organizations.

Activities and games that use dot patterns, dice, dominos, fingers, or five- and ten-frames can support students in subitizing.

Games to Promote Subitizing

Dot Bingo

This game provides the opportunity for students to subitize in a variety of ways. Bingo card representations include numerals, die dot patterns, raised fingers and five-or ten-frames. (Adapted from Lawson, pg. 159)

Dot Bingo Game Instructions (English)

Dot Bingo Cards - Lawson (English)

Roll & Cover Activity

This game provides the opportunity for students to subitize in a variety of ways. Roll & Cover cards show different number representations include numerals, rekenreks, raised fingers and five-or ten-frames.

Roll & Cover activity instructions (English)

Roll & Cover activity cards (BLM) (English)

Roll & Cover activity cards (BLM) (French)

I Spy Game

This game provides the opportunity for students to subitize in a variety of ways. Using one deck of players cards face up, students will play the game I Spy.

I Spy game instructions (English)

Alternate Playing Card options (English)

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