Coffee filters come in different sizes. This depends on the number of cups of coffee you want to brew. Common sizes include size 1 for 1 to 2 cups, size 2 for 1 to 4 cups, and size 4 for 8 to 10 cups. The right filter size depends not only on the number of cups, but also on the type of coffee maker. Coffee filters for different coffee makers, such as the hand filter, Aeropress, traditional coffee maker, or Chemex, vary. For the Aeropress and Chemex, as well as for some coffee makers, you need special, custom-fit filters from the manufacturer.