Help your 3rd grade students confidently find perimeter by adding side lengths with this comprehensive math lesson plan resource. This perimeter lesson plan introduces perimeter as the distance around a shape, helping students distinguish between area and perimeter while learning how to calculate it for rectangles and other polygons. Designed for introduction, guided notes practice, and review, this scaffolded lesson works seamlessly for whole-group instruction, interactive practice, sub plans, supplemental practice, review lessons, and print or digital classrooms.

Understanding perimeter can be challenging because students often confuse it with area. This lesson provides explicit modeling and structured practice so students learn to focus on the edges of a shape rather than the space inside, and understand that perimeter is found by adding all side lengths.

Teachers will love that everything is fully editable, making it easy to adapt pacing, examples, or activities to meet your classroom’s needs, whether you teach paperless, print-based, or a mix of both.

What’s Included:

This complete perimeter lesson includes both teaching and student materials:

• Printable lesson plan with pacing, prompts, and instructional notes
• Editable Google Slides presentation for instruction (includes speaker notes aligned to the lesson plan)
• Interactive guided practice slides for students to follow along
• Printable guided practice version for print-based classrooms
• Independent practice worksheet (perfect for homework or extra in-class practice)
• Exit ticket and reflection prompts
• Answer keys for all student practice

How to Use It:

Teach this lesson during your geometry or measurement unit or as targeted instruction for finding perimeter. Present the lesson using the Google Slides, model strategies using the guided examples, and allow students to practice using the interactive slides or printable pages.

Because the resource is fully editable, you can:

• Choose digital, print, or hybrid formats
• Adjust examples or pacing
• Use it for whole group, small group, or reteaching
• Assign practice as classwork or homework

Standards Alignment:

CCSS.MATH.CONTENT.3.MD.D.8

Solve real world and mathematical problems involving perimeters of polygons, including finding the perimeter given the side lengths, finding an unknown side length, and exhibiting rectangles with the same perimeter and different areas or with the same area and different perimeters.

This lesson focuses on finding the perimeter of shapes by adding side lengths, including rectangles with unknown sides and other polygons.

Save planning time and give your students the structured support they need to understand finding perimeter. Download this editable, ready-to-use lesson and teach with confidence!

Want the next lesson on Real-World Perimeter Problems? 

Grab it here → Real-World Perimeter Problems & Comparing Perimeter | 3rd Grade Math Lesson Plan

Teach the entire unit on Geometry: Area & Perimeter with a money saving bundle!

Grab it here → 3rd Grade Geometry: Area & Perimeter Full Math Unit | 2D Shapes, Area, Perimeter