Volume: how much space is inside a solid
In 5th grade, children learn what volume is: the amount of space inside a solid, measured by how many same-size cubes fill it with no gaps or overlaps.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 5th grade practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
Hana stacks 12 unit cubes into a tall tower. Then she takes it apart and uses all 12 cubes to build a long, low wall. How does the volume of the wall compare with the volume of the tower?
- They have the same volume
- The tower has more volume
- The wall has more volume
Why this matters
Volume is the third kind of measuring your child meets, after length and area, and keeping the three straight will help them for years. Knowing that volume counts cubes filling a space is what makes the length × width × height formula later this year make sense. It also answers everyday questions like how much a box, a fish tank, or a bag of soil will hold.
Where kids can get stuck
- Confusing volume with area, counting the squares on one face of a box instead of the cubes inside.
- Ignoring gaps and overlaps, estimating a box's volume by tossing in cubes loosely and counting them.
- Assuming the taller container always holds more, when a short, wide box can hold more than a tall, narrow one.
How you can help
- Pack a small box with sugar cubes, dice, or building blocks. Ask your child how many fit with no gaps, and talk about why packing them tightly matters for measuring volume.
- Compare two containers in the kitchen, such as a tall glass and a wide bowl. Ask which one your child thinks holds more, then fill one with water and pour it into the other to check.
- While building with toy blocks, ask your child to make two different shapes using the same number of blocks. Talk about how they have the same volume even though they look different.
Bobby's Math Club offers free practice that grows with your child.
Questions parents ask
Why is my child learning volume with cubes first?
Cubes make volume something your child can see and count. Packing a box with unit cubes shows that volume means filling a space, which is different from measuring a length or covering a surface. Once that idea is clear, the formula length × width × height makes sense, because it is a quick way of counting the cubes.
What is the difference between area and volume?
Area measures a flat surface, like the floor of a room, using squares. Volume measures the space inside a solid, like a cardboard box, using cubes. A box's bottom might have an area of 6 square units, while the whole box might have a volume of 12 cubic units if it is 2 cubes tall.
What does "cubic unit" mean?
A cubic unit is the volume of a cube with edges 1 unit long. If each edge is 1 centimeter, it is a cubic centimeter. If each edge is 1 inch, it is a cubic inch. Saying a box has a volume of 24 cubic inches means 24 of those inch cubes would fill it exactly.
Make learning math fun
Bobby's Math Club turns 5th grade math practice into something fun to do together.
- Free, unlimited practice for every child in your family
- A few minutes a day, at just the right level
- Level-ups, badges, and a cheer for every win
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
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Join the clubNote for teachers: This skill is covered by Common Core math standard 5.MD.C.3: “Recognize volume as an attribute of solid figures and understand concepts of volume measurement. a. A cube with side length 1 unit, called a "unit cube," is said to have "one cubic unit" of volume, and can be used to measure volume. b. A solid figure which can be packed without gaps or overlaps using n unit cubes is said to have a volume of n cubic units.” Learn how Bobby's Math Club can help your students grow. (Common Core 5.MD.3)