One teaspoon will fill about 7 - "0" capsules. The weight depends on the density of the powder you are using. Some powders are much denser than others. It also depends on the fineness of the powder. The only way to be sure is to check the weight of each individual material.
On a scale accurate to within one-tenth of a gram or even to one-tenth of an ounce or even to a gram, you can weigh 24 empty capsules and then compare with the weight when full. If you only want a small amount of active ingredient, then you can mix with a material such as milk powder or rice powder as a filler. That way you can use "0" size capsules with various weights of active ingredients.
Ingredients: Beef gelatin and water.
No preservatives and no additives!