Cardboard Coin Sorter

What You’ll Create

Ka-ching! 🪙 Your young engineers will build a real working coin sorting machine from a cardboard box! Cut slots of increasing size into a ramp inside the box — small coins fall through the first slot, medium coins through the second, and large coins roll to the end. Drop a handful of mixed coins in the top and watch them sort themselves by size. It’s like magic, but it’s engineering!

How to Set It Up

Step 1: Prepare the Box

Find a cardboard box (a shoebox is ideal). Stand it on its side so the open end faces up. Use scissors and a ruler to measure and mark where you’ll cut the coin slots. You need a ramp inside the box — cut a piece of cardboard to fit diagonally from near the top to the bottom. ⚠️ Adult Helper Needed for cutting. 📦

Step 2: Cut the Sorting Slots

Cut slots in the ramp piece, starting with the narrowest. Measure your actual coins — the smallest coin needs the first slot, the next size gets the second slot, and so on. Cut each slot just slightly wider than its target coin. Make 3–4 slots, each a bit bigger than the last. Use a ruler to keep them straight. 📏

Step 3: Assemble the Machine

Glue or tape the ramp inside the box at a slight angle (so coins roll down). Add cardboard dividers below each slot to create collection compartments. The coin enters at the top, rolls down the ramp, and drops through the first slot it fits through! Test with actual coins and adjust. 🔧

Step 4: Test and Label

Drop different coins in one at a time to test your sorter. Do small coins fall through the first slot? Do large coins pass over all the small slots? Adjust any slots that are too tight or too wide. Use markers to label each compartment and decorate your machine! 🏦

Have fun!

• 💰 Sort all the coins in the house — how much money is there in total?
• 🏦 Build a slot in the top to make it a combined sorter and piggy bank!
• 📊 Count how many of each coin type you have — make a bar chart!
• 🔬 Experiment with coins from different countries — will they sort correctly?

Why It’s Amazing

• Engineering Design: Building a machine with moving parts that actually works is authentic engineering — designing, building, testing, and iterating. ⚙️

• Measurement Skills: Measuring coin diameters precisely and cutting slots to match teaches practical measurement and the importance of accuracy. 📏

• Maths Connection: Sorting, counting, and totalling coins naturally incorporates addition, multiplication, and understanding of monetary value. 🔢

• Problem-Solving: When a coin gets stuck or goes to the wrong slot, troubleshooting develops critical thinking and patience. 🧠

Pro Tips

For ages 5–7: An adult should do the cutting. Let the child measure the coins with a ruler and help decide slot sizes. Focus on the excitement of testing — the moment a coin rolls and drops perfectly is incredibly satisfying!

For ages 7–10: Let them measure and mark the slots themselves. Guide them through the logic — why does the smallest slot come first? What happens if you put the biggest slot first? Discuss how real coin-counting machines work.

For ages 10–12: Challenge them to build a completely enclosed machine with only an input slot at the top and labelled output trays at the bottom. Can they add a coin counter mechanism? Research how banks sort millions of coins.

Secret Pro Move: Cover the ramp with smooth packing tape — coins will slide much more smoothly than on rough cardboard, making the sorting action faster and more reliable! 🎯