Spread the shells on a baking sheet. Bake at 225F for 20 minutes to dry them out. Using a coffee or spice grinder, grind the shells to a very fine powder. You can also use a blender for this, but I find that a coffee grinder makes the finest powder, so you don't have any large eggshell pieces in your smoothie.

How long does it take to make eggshell powder?

Bring a medium pot of water to a boil. Add the eggshells and cook for 2 minutes. Remove the shells from the water and transfer to a baking sheet. Bake the shells for 45–50 minutes, until they are completely dried out.

Can you make your own calcium powder?

In a blender or coffee grinder, grind the eggshells until they become a fine, white powder. Take the calcium. Take your homemade eggshell calcium however you prefer— with food, with water, or by itself. Half a teaspoon of the powder equals about 400 milligrams of calcium.