Build a Compass

Magnets are fun! Magnet experiments in Science class always get a thumbs-up from kids. There are so many fun experiments that can be done with just a few simple magnets and metal objects to discover how they work. And this compass building project is one of those. With just a few household materials, you can learn how to build a compass that really works! But before we begin, let’s take a look at a few magnet facts that would be good to know while doing this project:

  • The Earth’s core is believed to be a mix of iron and nickel, giving the Earth its own magnetic field.
  • Magnetic compasses use the Earth’s magnetic field to navigate in all directions (north, south, east, and west).
  • Magnets do not attract glass, plastic, or wood.
  • Iron, nickel, and cobalt are metals that are attracted to magnets. Most other metals are not attracted to magnets.

Now that we’ve learned some new magnet-related tidbits, let’s get started!

Materials Needed:

A needle (or hairpin, straightened paper clip, straightened safety pin, or other piece of metal that can be magnetized)

A magnet

Small, round piece of cork (or craft foam, bottom of Styrofoam coffee cup, cap from milk jug, or other object that floats)

Non-metallic bowl



  1. Stroke your needle (or other metallic object) against your magnet 20-40 times to magnetize it. Be sure to stroke it in only one direction and NOT back and forth. Stroke it one way, lift it up, and repeat.
  2. Pour water into your bowl.
  3. Place the small, round object (cork, Styrofoam piece, milk jug cap) in the center of the bowl of water. Try to keep it away from the edges of the bowl.
  4. Set your magnetized needle in the center of the floating object.
  5. Watch as the needle slowly starts to turn in the bowl of water so that it ends up pointing north to south.
  6. To check the accuracy of your new homemade compass, set a compass next to the bowl to see if the needles both point north. Or use a compass app on your smart phone, such as Smart Compass or Compass°.
  7. If your homemade compass isn’t cooperating, stroke the needle against the magnet again to re-magnetize it and set it back on your floating object.

How Does It Work?

Well, I’m sure you’re wondering how this works. It’s so simple, yet so accurate. How can it be? Well, the answer is simple too!

When you stroke your needle against the magnet, the needle becomes magnetized. This happens because the electrons in the needle straighten up and align themselves with the magnet as you stroke it. The magnetic needle then aligns itself with the Earth’s magnetic field when it’s placed on top of the water. The bowl of water creates an almost frictionless bearing so that the object and magnetized needle can float freely. Magnetizing, isn’t it?