Kindergarten · K.G.A.3

3D shapes in kindergarten

3D shapes are solid shapes you can hold, like a ball, a box or a can. In kindergarten, your child learns to tell them apart from flat shapes, the ones that lie on a page. Telling 2D and 3D shapes apart comes before learning all their names.

What the standard says

The official Common Core wording, quoted exactly. The plain version follows.

K.G.A.3 Identify shapes as two-dimensional (lying in a plane, "flat") or three-dimensional ("solid").

What it means, in plain words

A flat shape lies on a page, like a circle or a square drawn with a crayon. You can draw it and trace around it, but you cannot pick it up. Schools call flat shapes 2D shapes. 2D is short for two-dimensional: the shape goes across and up and down, but it has no thickness.

A solid shape takes up space. You can hold it, turn it and look at it from different sides. Schools call solid shapes 3D shapes, because they also go back, away from you. The 3D shapes kindergarten children meet most often are the cube (like a toy block), the cone (like an ice cream cone), the cylinder (like a soup can) and the sphere (like a ball).

Sorting flat and solid shapes in kindergarten is about seeing the difference. The names of the shapes can come later. A child who says "I can only draw this one" and "I can pick this one up" has the idea. Very thin things, like a sheet of paper, are usually sorted with the flat shapes.

Your child should be able to:

Say whether a shape is flat or solid
Sort a mix of drawn shapes and real objects into a flat group and a solid group
Use the words flat and solid, or 2D and 3D, to describe a shape
Find a solid shape at home and say why it is solid

Example

Your child sees a triangle drawn on paper and a can of beans. Which one is flat and which one is solid?

The triangle lies on the paper. You can trace around it, but you cannot lift the triangle off the page.
The can stands on the table. You can hold it and turn it around.
The triangle is flat, a 2D shape. The can is solid, a 3D shape called a cylinder.

Where children usually get stuck

Your child calls a ball a circle and a box a square.
The outline of a ball looks like a circle, and one side of a box looks like a square. The child names the outline, not the whole solid shape.
What helps. Hold a ball over a sheet of paper and trace around it. Put the ball next to the drawing and ask which one you can pick up.
Your child sorts by size: big things go with the solid shapes and small things go with the flat ones.
Big and heavy things feel more solid to a young child. Size has nothing to do with it. A tiny bead is solid, and a big drawing on a poster is flat.
What helps. Put a bead next to a large drawing. Ask which one your child can hold in one hand, then which one is flat.
Your child says a sheet of paper is solid because it can be picked up.
The child learned the rule "solid things can be held", and paper can be held. Kindergarten counts things as thin as paper as flat.
What helps. Add a second question to "Can I hold it?": "Is it thick, or thin like paper?" Compare a sheet of paper with a book, and sort the paper with the drawings.

Try four practice questions

Real kindergarten questions from our question bank, easiest first. Answer them right here, check each one, and see a worked solution for any question.

1Warm-up
Drag each shape into the bin that matches: Flat or Solid.
Drag each item into the group where it belongs, or tap the item, then tap the group.
Flat
Drag or tap items here
Solid
Drag or tap items here
Keyboard instructions: focus an item and press Enter or Space to pick it up. Move focus to a bin or the bank and press Enter or Space to drop it. Press Escape to cancel.
Show the answer and how to solve it
Flat bin: circle. Solid bin: cube.
1. 1Look at each shape. Flat shapes can be drawn on paper. Solid shapes take up space, like things you can hold.
2. 2The circle is flat. It goes in the Flat bin.
3. 3The cube is solid. It goes in the Solid bin.
Common mistake. A common mistake is to put the cube in the Flat bin. A cube is solid — it takes up space like a block. A circle is flat — you can draw it on paper.
The idea underneath. Flat shapes can be drawn on paper. Solid shapes are like things you can hold, such as a ball or a block.
2On level
Look at the photos below. Pick every object that is solid.
A
B
C
D
Show the answer and how to solve it
The soccer ball and the lego brick are solid. The dollar bill and the sticker are flat.
1. 1Look at each photo. Decide: is it flat, or is it solid?
2. 2The soccer ball takes up space — it is solid. The lego brick is a small block that takes up space — it is solid. The dollar bill is thin — it is flat. The sticker is thin — it is flat.
3. 3Pick the soccer ball and the lego brick.
Common mistake. A common mistake is missing the lego brick because it is small. Small things can still be solid — the lego brick has many sides and takes up space.
The idea underneath. A solid object takes up space. You can touch many sides of it. A flat object is thin like paper.
3On level
Look at the photos below. Pick every object that is flat.
A
B
C
D
Show the answer and how to solve it
The postcard and the playing card are flat. The orange and the eraser are solid.
1. 1Look at each photo. Decide: is it flat, or is it solid?
2. 2The orange has a solid shape. The postcard is very thin. We call it flat. The eraser has a solid shape. The playing card is very thin. We call it flat.
3. 3Pick the postcard and the playing card.
Common mistake. A common mistake is picking the eraser. The eraser is solid — it is a small block that takes up space. Look for objects that are thin like paper.
The idea underneath. We call a very thin object flat. A ball or a box has a solid shape.
4Stretch
James looked at a dice.
James says it is flat. Is James correct?
A
Yes
B
No
Show the answer and how to solve it
No — James is not correct. The dice is solid because it has thickness, not flat like James said.
1. 1Look at the dice in the picture.
2. 2A dice has thickness — you can hold it in your hand. It has space inside. So a dice is solid.
3. 3James said the dice is flat. That does not match what the dice really is!
4. 4So James is not correct. The answer is No.
Common mistake. A common mistake is thinking a dice is flat because it has flat sides. But having flat sides does not make it flat — the dice still has thickness. That makes it solid.
The idea underneath. Solid means it has thickness; flat means paper-thin. To check a classmate, look at the object yourself, then compare to what they said.