Using Informal Units to Measure LengthActivities & Teaching Strategies
Active learning works because young children develop spatial reasoning best through physical movement and hands-on materials. Handling objects like blocks or paperclips lets students feel the direct relationship between unit size and count, turning abstract ideas into tangible understanding.
Learning Objectives
- 1Compare the lengths of different objects using informal units.
- 2Measure the perimeter of simple polygons by counting informal units.
- 3Explain why using different informal units results in different measurement counts.
- 4Demonstrate how to measure a length without gaps or overlaps.
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Partner Chain: Measuring Books
Pairs select classroom books and measure perimeter using linking cubes laid end-to-end. They count units for each side, add totals, then switch units like hands for comparison. Record findings on charts and discuss differences.
Prepare & details
How many blocks long is this book?
Facilitation Tip: During Partner Chain: Measuring Books, circulate and gently nudge pairs to slide blocks together so they touch but do not overlap.
Setup: Varies; may include outdoor space, lab, or community setting
Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework
Shape Hunt: Perimeter Paths
In small groups, students find polygons like windows or drawings, trace outlines on paper, and cover with straws or fingers. Count units per side and total perimeter. Share results, noting irregular shapes.
Prepare & details
Can you measure the table using your hands?
Facilitation Tip: For Shape Hunt: Perimeter Paths, demonstrate how to trace the outline first with a finger before placing paperclips along the edge.
Setup: Varies; may include outdoor space, lab, or community setting
Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework
Unit Swap Challenge: Whole Class
Display a long rope; class measures perimeter using blocks first, records count, then repeats with larger units like feet. Tally results on board and graph comparisons to spot patterns.
Prepare & details
Why might we get a different answer if we use different-sized objects to measure?
Facilitation Tip: In Unit Swap Challenge, pause the class after the first round to ask which unit felt easier to use and why.
Setup: Varies; may include outdoor space, lab, or community setting
Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework
Build and Measure: Individual Mats
Each student builds irregular polygons with toothpicks on mats, then measures perimeter using beads. Adjust for full coverage, recount, and label drawings with unit counts.
Prepare & details
How many blocks long is this book?
Facilitation Tip: During Build and Measure: Individual Mats, provide small sticky notes so students can mark where each unit ends, keeping their place as they iterate.
Setup: Varies; may include outdoor space, lab, or community setting
Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework
Teaching This Topic
Teach this topic by letting students experience measurement mistakes first. Use clear, short language like ‘touch to edge, no gaps, no overlaps’ instead of abstract rules. Research shows children refine their understanding when they notice inconsistencies themselves, so plan time for them to compare their counts with classmates after each measurement.
What to Expect
By the end of these activities, students will line up units without gaps or overlaps, explain why unit size affects the total count, and measure perimeters of simple polygons using informal units. They will compare measurements with peers and adjust their techniques based on feedback.
These activities are a starting point. A full mission is the experience.
- Complete facilitation script with teacher dialogue
- Printable student materials, ready for class
- Differentiation strategies for every learner
Watch Out for These Misconceptions
Common MisconceptionDuring Unit Swap Challenge, watch for students who assume the larger block will always give a smaller count because it feels heavier or takes more space in their hand.
What to Teach Instead
After the first round, ask each group to display their measurements side by side so students see that fewer large blocks fit along the same edge compared to small ones, prompting them to verbalize the inverse relationship.
Common MisconceptionDuring Partner Chain: Measuring Books, watch for overlaps or visible gaps between blocks.
What to Teach Instead
Have students remove the blocks and look at the pencil marks left behind, then re-place the blocks with the teacher modeling how to slide each one snugly against the next without pushing over the edge.
Common MisconceptionDuring Shape Hunt: Perimeter Paths, watch for students who include the inside of the shape or skip edges entirely.
What to Teach Instead
Ask students to trace the edge with one finger while counting aloud, emphasizing ‘around the outside only,’ and have partners verify by holding the paperclips along the traced line.
Assessment Ideas
After Partner Chain: Measuring Books, give each pair a different book and ask them to measure it using paperclips. Circulate with a checklist noting whether units are placed end-to-end without gaps or overlaps and whether they record the count accurately.
During Unit Swap Challenge, collect each student’s recorded measurements for the same object using two different units. Check if they wrote the count next to the correct unit and if they can explain in one sentence why the counts differ.
After Build and Measure: Individual Mats, ask students to hold up their mats and share one thing they noticed while measuring. Listen for language like ‘more small units’ or ‘fewer big units’ to assess their grasp of unit size affecting the total count.
Extensions & Scaffolding
- Challenge: Provide a curved shape cut from card and ask students to estimate how many paperclips would cover its perimeter, then test their guess.
- Scaffolding: Give students a strip of masking tape to place along the edge before measuring, ensuring they cover the line completely.
- Deeper exploration: Ask students to create their own irregular polygon from tape on the floor and measure it using three different informal units, recording differences in counts on a simple chart.
Key Vocabulary
| Length | The measurement of how long an object is from one end to the other. |
| Perimeter | The total distance around the outside edge of a shape. |
| Informal Unit | A non-standard object used for measuring, such as blocks, hands, or paperclips. |
| Measure | To find out the size or amount of something, like length, using a unit. |
Suggested Methodologies
Planning templates for Mathematics
5E Model
The 5E Model structures lessons through five phases (Engage, Explore, Explain, Elaborate, and Evaluate), guiding students from curiosity to deep understanding through inquiry-based learning.
Unit PlannerMath Unit
Plan a multi-week math unit with conceptual coherence: from building number sense and procedural fluency to applying skills in context and developing mathematical reasoning across a connected sequence of lessons.
RubricMath Rubric
Build a math rubric that assesses problem-solving, mathematical reasoning, and communication alongside procedural accuracy, giving students feedback on how they think, not just whether they got the right answer.
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