How to Make a Lego Catapult with Bricks You Already Have

This LEGO catapult design uses common LEGO pieces that you have already or could substitute a similar block. Kids of all ages can use the simple LEGO catapult idea and make working catapults at home or in the classroom. This simple STEM project is playful learning at its best!

Catapult made out of LEGO bricks finished and sitting on green background
Let’s make a LEGO catapult!

Homemade Catapult DEsign

Last week my family visited a Genghis Khan Exhibit and saw a real life size trebuchet that they could put their hands on (and shoot some ping pong balls across the museum).  At home, they have been all about creating catapults out of everything.

Related: 15 more ideas how to make a catapult

This LEGO catapult design was created by my 10 year old using just the bricks we already have.

The boys own one of the Lego Castle sets that includes a catapult. Many of the pieces used were from that set.  He has modified that a little to increase projectile distance.  

As with all things Lego, modify these instructions to use pieces that you might have at home!

How to Make a Lego Catapult

Step 1  

Construct the base.   The base platform and the catapult foundation consist of these pieces:

Lego catapult building step 1
These are the pieces we used for the catapult base

Step 2  

Add Lego blocks that allow for arm movement.  

The base built from pieces pictured above are on the left. The pieces used for the arm movement base are pictured on the right:

Lego catapult building step 2
Pictured on right are the pieces used to make the catapult arm move

Step 3

The base is now complete.   

You can see that the two small 2 x 1 stud bricks in between the gold caps are on a rod and can be rotated 360 degrees at this point.   This is where the moving arm will attach:

Lego catapult building step 3
This is the completed LEGO catapult base

Step 4

Build the catapult’s moving arm with the pieces shown here or similar:

Lego catapult building step 4
Now it is time to create the catapult’s swinging arm

Step 5

Finish the arm and attach it to the 2 x 1 bricks mentioned above:

Lego catapult building step 5
This is what the LEGO catapult arm looks like from the side

Step 6

Attach a rubber band.

Finished Lego catapult
The rubber band wraps around the side wheeled posts and the bottom 4 post circle

Step 7

Launch projectiles across the living room.

lego catapult final image
This is what it looked like when we were done.

Catapult vs. Trebuchet

The exhibit was calling this type of catapult a trebuchet.

We were wondering what the difference between the two weapons were and after a little internet search which included Wikipedia, this is what I understand to be true:

  • Catapult:   A catapult is a mechanical device used to hurl objects.   It is a general term and there are many types of catapults.
  • Trebuchet:   A trebuchet is a type of catapult.   The early models were called traction trebuchets and used manpower and ropes to launch a projectile.   Later models used pulleys and counterweights and improved the accuracy of aim significantly.

The type of catapult we just built out of Legos could be described as a traction trebuchet if you imagined the rubber band to be men pulling on ropes.

Looking for more trebuchet and catapult building ideas? 


More LEGO Fun from Kids Activities Blog

How did your lego catapult turn out?  How far can you launch projectiles across the room?


  1. ryan ……….. nice intelligent, hopefully Ryan can make more than the past …. ok


  2. What a great idea and thank you for making it so simple to follow the directions. I’m going to show this to my son later tonight and see what kind of embellishments he adds to the catapult. I know I’ll be finding more little Lego pieces in the carpet after the catapult session.

    Sue Kirchner
    Chief Fun Officer – 51 Summer Family Fun Activities!

  3. This is made of awesome. My daughter is going to go nuts for it when I show her tomorrow. Way to go Ryan!

  4. My kids will love this! They are Lego maniacs! Can’t wait to show them. Thanks for sharing.

  5. How fun! We made a catapult with boxes earlier this year, and lego one would be a great follow-up. I am excited to show my kids.

  6. Oh that’ is awesome! I hope we have all the parts to make this, I know my son is totally going to want to do this!

  7. My boys will LOVE this. I’m not sure if I should show them or not, I’m having visions of lego fights and legos flying all over the house. šŸ™‚ Great idea, Ryan!

  8. What a great idea. My children love building out of lego, I’m sure they’ll want to give this a go.

  9. This is awesome! My son just made a catapult at scouts day camp, but I think he would love to have this one too!

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