Pound cinnamon sticks with a hammer or meat tenderizer to make smaller pieces.
In a clean coffee grinder or spice grinder, combine cinnamon stick pieces, whole cloves, whole allspice and grind into powder. Leave it in the grinder and set aside.
Grate the nutmeg on a nutmeg grater or microplane. Measure 1½ to 3 teaspoons of fresh nutmeg, depending on your preference, and add it to the grinder.Add the ground ginger to the grinder at this time, too.
Give everything a whirl in the grinder to combine.
Store mix in tightly sealed jar until ready to use.
Notes
Pumpkin spice will keep well in an airtight container for up to 1 year. The fresher it is when you use it, the more intense the flavor will be.