Perimeter Worksheet

Perimeter is the distance all the way around the outside of a flat shape, and this perimeter worksheet gives third graders a clear, hands-on way to find it. Students begin by counting the units around figures drawn on a grid, which makes the idea concrete before any formula appears. They then move to polygons with the side lengths labeled, adding every side to find the total distance around. Working both ways helps children understand that perimeter is always a sum of side lengths, whether they count the units themselves or read the measurements from the picture.

This printable perimeter worksheet is ready to use in class, in a small group, or at the kitchen table. Part A asks students to count the units around four figures on unit grids, including an L-shape and a shape with a notch, so children learn to track every edge instead of guessing. Part B gives three labeled polygons, a rectangle, a square, and a triangle, with centimeter measurements on every side. Part C is a real-world fence problem that asks students to explain their thinking. Use this 3rd grade geometry worksheet as guided practice, morning work, a math center task, or a quick check before a unit test.

What’s Included

• 1 print-ready PDF worksheet
• 4 grid figures for counting units around the edge
• 3 labeled polygons for adding side lengths in centimeters
• 1 real-world word problem with space to explain the answer
• A complete answer key

Practicing this way helps kids in three important ways. First, counting units around a figure builds a mental picture of what perimeter really means, so the idea sticks long after the lesson. Second, adding labeled side lengths strengthens multi-digit addition while students work on geometry, so two skills grow at once. Third, the fence word problem asks children to explain how they found the answer, and putting reasoning into words is exactly what standardized tests and classroom discussions ask third graders to do.

Teachers and parents can stretch this lesson in simple ways. Hand students a piece of string and let them measure the perimeter of a desk, a book, or a lunch tray, then compare their answers. Draw shapes on graph paper and trade papers with a partner to check each other’s counting. Walk the edge of a playground or a garden bed outside and count steps to feel perimeter with your whole body. Ask children to build a shape with square tiles and then find a different shape with the same perimeter, which quietly introduces the difference between perimeter and area.

Related Resources

• Solving Perimeter Word Problems Worksheet
• Perimeter Area Worksheet
• Finding Perimeters Word Problems Worksheet
• Shapes Song by Have Fun Teaching