At Milk Street, whenever possible, we prefer to buy whole spices rather than ground spices. Oxidation can cause store-bought ground spices to lose flavor quickly and can also contribute stale, off flavors to a dish. Whole spices stay fresh longer and pack more flavor, whether used whole or ground as needed. And they can remain fresh stored in a cabinet for up to two years (ground spices last about six months, at most).
The only trouble is knowing how much to pulverize when a recipe calls for ground. We hate to be wasteful and grind too much, and few recipes do the conversion for us. So we decided to take the mystery out of this kitchen quandary and suss out equivalencies for 15 whole and ground spices. Some spices yielded larger volumes when ground because of aeration that occurs during grinding.