How Big Were Dinosaurs?

Part of the Dinosaurs: Activities and Lesson Plans Curriculum Collection.


In the Roosevelt Memorial Hall at the American Museum of Natural History, a Barosaurus rears up to a height of 50 feet as it protects its offspring from an Allosaurus attack. Some dinosaurs, such as the Barosaurus, were quite large and may have weighed as much as 35 tons. But other dinosaurs, such as Compsognathus, were about the size of a chicken and weighed only eight pounds.


In this activity, students will begin to explore the size of the large dinosaurs by comparing their feet to the foot of a large Apatosaur.


  • Construction paper
  • Safety scissors
  • Crayons
  • Glue
  • An Apatosaur footprint was approximately 24” by 48”. Use chart paper and the footprint outline on the next page to create a footprint of this large dinosaur. 


  1. Ask students to name some of the dinosaurs they know and to describe how big they were. Suggest that they compare the dinosaur’s size to known objects, such as a school bus, house, building, etc.
  2. Display the footprint and explain that it is the approximate size of a footprint of Apatosaur, a dinosaur that was about 90 feet long and weighed about 35 tons. Tell students they are going to compare their footprints with that of the large dinosaur.
  3. Have students work with a partner. Distribute construction paper, crayons, and scissors to the class. Have each student trace their own footprint on the construction paper and cut it out. Allow students time to compare their individual footprints with the dinosaur footprint.
  4. Ask students to estimate how many of their footprints would fit in one footprint of an Apatosaur. Write the various estimates on the board. Tape the Apatosaur footprint to the chalkboard. Call on students, one at a time, to glue their footprint on the Apatosaur footprint. Make sure students glue the footprints right next to each other so that there is no wasted space. When the footprint is filled, have students count how many of their prints it took to fill the dinosaur footprint. Check the results against students’ estimates.
  5. Remind students that while many dinosaurs were huge, there were also many that were small. 
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