When substituting dried herbs for fresh, use 1/3 the amount of fresh herbs the recipe calls for. For example, if a recipe calls for 1 tablespoon of fresh herb, use 1 teaspoon of dried herb. Alternatively, triple the amount of fresh herbs if the recipe calls for dried.
Substitutions aren't always appropriate. For soups or stews that simmer for a prolonged period of time, always used dried herbs, because fresh herbs lose their flavor when they cook for too long. It's best to add fresh herbs near the end of cooking or just before serving. Also, use fresh herbs when serving the herbs raw, such as with basil in brushchetta or dill in potato salad.
When using dried herbs instead of fresh, make sure the dried herbs are in peak condition. Dried herbs are more concentrated than fresh, but they can go stale if they are old or improperly stored. Check for freshness by looking at the color and testing the aroma. If the herb's color looks faded, or it has very little aroma when you crush a small amount in your hand, the herb is too old to provide optimum flavor. Store dried herbs in an air-tight container in a cool, dark place.