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Common Core Math3rd GradeMeasurement & Data

3.MD.5: Understand Area as Unit Squares

Also written as 3.MD.C.5 and CCSS.MATH.CONTENT.3.MD.C.5 · Cluster: Geometric measurement: understand concepts of area and relate area to multiplication and to addition.

Make 3.MD.5 Graph PaperAll 25 3rd Grade Math Standards

The Official Wording

Recognize area as an attribute of plane figures and understand concepts of area measurement.

Common Core State Standards, Grade 3, Measurement & Data · Read it at the source · Checked October 14, 2026

What 3.MD.5 Means in Plain English

Third graders learn what area measures before they count it. A unit square, 1 unit on each side, is worth one square unit (part a). If 12 unit squares cover a shape with no gaps and no overlaps, the shape has an area of 12 square units (part b).

Area is new in 3rd grade, though splitting rectangles into rows of squares started in 2.G.2. Next, students count squares in real units (3.MD.6) and connect the count to multiplying the sides (3.MD.7). Fourth grade applies the area formula to real problems (4.MD.3).

3.MD.5 I Can Statements

  • I can explain what a unit square is.
  • I can tell that area counts squares with no gaps or overlaps.
  • I can show that two different shapes can have the same area.

3.MD.5 Worked Example

Two garden plans that look nothing alike, measured the way parts a and b describe: by the unit squares that cover them.

Problem

Two garden plans are drawn on square-inch grid paper. Plan A is a long strip, 2 squares by 6. Plan B is an L-shape: a 2 by 4 block with a 2 by 2 block beside its bottom. Leo says Plan A is bigger because it is longer. Is he right?

Which garden plan is bigger?
  1. Name the unit. Each grid square is 1 inch on every side, a unit square, so each one is worth 1 square inch.1 unit square = 1 square inch (part a)
  2. Check the covering. Grid squares fit edge to edge, so nothing inside either plan is left uncovered and no square sits on another.no gaps, no overlaps
  3. Count Plan A square by square, marking each one as it is counted.Plan A: 12 square inches
  4. Count Plan B the same way, the 2 by 4 block and then the 2 by 2 block.Plan B: 8 + 4 = 12 square inches (part b)
AnswerNo. Both plans have an area of 12 square inches, even though Plan A is longer.

Check it: Cut Plan B out and rearrange its 12 squares into a 2 by 6 strip. It covers Plan A exactly, square for square.

Common Mistakes with 3.MD.5

Longer means bigger

A 2 by 6 strip called bigger than a 3 by 4 rectangle because it reaches farther

Try this: Cover both shapes with the same tiles and count. Area is how much surface is covered, not how far a shape stretches.

Gaps and overlaps

Round counters with spaces between them used to cover a shape, giving 9 for a shape that needs 12 squares

Try this: Use only square tiles, pushed edge to edge, and ask whether any desk shows through or any tile sits on another.

Counting only the border

A 3 by 4 rectangle given an area of 10 because only the squares along the edge were counted

Try this: Shade each square as it is counted, the middle ones too, so nothing is skipped and nothing is counted twice.

Where 3.MD.5 Fits

Comes Before2.G.2Split a rectangle into rows and columns of same-size squares and count them.1.MD.2Measure length with same-size units laid end to end, no gaps or overlaps.
Alongside3.MD.6Measure areas by counting square centimeters, inches, feet and meters.3.G.2Split shapes into parts with equal areas and name each part as a unit fraction.
Comes Next3.MD.7Show that tiling a rectangle and multiplying its sides give the same area.4.MD.3Use the area formula for rectangles in real problems.

Practice 3.MD.5

Graph Paper GeneratorFree ToolSquare-inch grid paper. Students draw two shapes with the same number of squares and argue about which one is bigger.1 inch squaresOne pagePrint
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Math Worksheet GeneratorFree ToolArea practice at the 3rd grade level with an answer key: shapes drawn on a grid, measured by counting the unit squares inside.Grade 3AreaAnswer key
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Quick Check

  1. A shape is covered by 15 unit squares with no gaps or overlaps. What is its area?
  2. Sam covers a shape with 8 round counters and says its area is 8 square units. Is he right?
  3. Shape A and Shape B each take 9 unit squares to cover, but they look different. Which has more area?

3.MD.5: Other Names

3.MD.53.MD.C.5CCSS.MATH.CONTENT.3.MD.C.5

Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved. Official wording from the Common Core State Standards PDFs at corestandards.org, last checked October 14, 2026. The explanation, I can statements, example, mistakes and practice on this page are EMStudio’s own, written beside the official wording. They are not part of the standard.