It happens all the time. You're almost done with a recipe, and suddenly see that it calls for fresh basil instead of dried, which is all you have on hand. Should you run to the store to buy fresh? If you use the dried, how should you measure it? Are dried herbs stronger than fresh?
Substituting fresh herbs for dry, or dry for fresh, is actually quite easy. You just need to know how to measure each kind, and keep in mind the basic ratio for dry vs. fresh herbs.
Read the recipe and note which herb, or herbs, the recipe calls for, and how much. Take note of whether it asks you to use dry or fresh herbs.
Do the math to convert your measurements. One tablespoon equals three teaspoons. The ratio of using dried herbs instead of fresh is one to three. One tablespoon of fresh herb equals one teaspoon of dried. Therefore, if the recipe asks for one tablespoon of fresh oregano, you may substitute one teaspoon of dried oregano. The reason for this ratio is that dried herbs are more concentrated than fresh.
Crush dried herbs in between your fingers and smell the herb. The dried herbs lose flavor quickly; if the scent is still strong, your herb is still strongly flavored. But if the scent is light, your herbs have lost flavor and you'll need to measure out slightly more than the recipe calls for. The herbs should also look nice and green, and not changed in color. Taste the dish after adding the herb, and add more as needed.
Be cautious of subbing dried herbs for fresh in some cases. If the recipe calls for using, for example, parsley as a garnish, you might want to skip using dried parsley, because garnishes are more decorative, and dried parsley won't look attractive. Likewise, using dry herbs instead of fresh or vice-versa may alter the texture of the dish undesirably.