Every cookbook gives you the same conversion: 1 tablespoon fresh = 1 teaspoon dried. Three to one. It's a clean rule, and it's also a half-truth. Drying a herb concentrates its essential oils as moisture leaves — but how much the oils concentrate, and how much they survive the drying process at all, depends entirely on which herb.
The 3:1 rule is roughly right for some herbs, way off for others, and a recipe for disappointment for a small group that shouldn't be dried at all.
The herbs the rule works for
- Thyme — fresh and dried are similar in potency; 3:1 is fine
- Oregano — dried is slightly more concentrated; 3:1 to 4:1
- Sage — dried holds well; 3:1 is fine
- Marjoram — dried slightly stronger; 3:1 to 4:1
These are the woody, tough-leaved Mediterranean herbs. Their essential oils survive drying well, and the rule was probably written about them.
The herbs where the rule lies
Rosemary. Dried rosemary is much stronger than fresh — 4:1 to 5:1 fresh-to-dried. Use less than the rule suggests. Also, dried rosemary leaves are wood-textured even after cooking; mince or grind them before using.
Bay leaf.Fresh bay leaves are almost flavourless; the leaf needs drying and ageing to develop its aroma. Most recipes assume dried bay even when they don't say so. The reverse rule: 1 dried = 1 fresh isn't a usable equivalence; just buy dried.
Basil.Dried basil tastes nothing like fresh — it loses the bright, almost peppery top notes and keeps only a faint hay-like base. The 3:1 rule technically works in terms of strength, but the flavour profile is so different that it's usually wrong to substitute at all. Use fresh basil where the recipe says fresh; pick a different herb if you only have dried.
The herbs that shouldn't be dried
Parsley, cilantro (coriander leaf), chives, dill, mint, tarragon. These are soft-leaved, water-heavy herbs whose flavour comes from volatile compounds that don't survive drying. The dried versions exist on supermarket shelves but they taste of dust.
Two practical responses: buy fresh and use within a few days, or freeze the leaves whole or in oil. Frozen dill, frozen parsley, and frozen cilantro are remarkably close to fresh. Dried, they're a different ingredient.
Aromatics aren't herbs
Dried garlic granules, dried onion flakes, ground ginger — these aren't herbs and they don't follow the 3:1 rule. The rough equivalences:
- 1 garlic clove ≈ 1 tsp jarred minced ≈ 1/2 tsp granulated ≈ 1/4 tsp powder
- 1 medium onion ≈ 1 cup chopped ≈ 1 tbsp dried minced ≈ 1 tsp powder
- 1 tbsp fresh ginger ≈ 1/4 tsp ground
Notice that the powder concentrations are far higher than 3:1 suggests — closer to 12:1. Dried aromatics also taste different from fresh: they're mellower, less sharp, and better in long-cooked dishes than in quick sautés.
How to read a recipe with this in mind
When a recipe specifies fresh and you only have dried (or vice versa), the 3:1 rule is a starting point, not the answer. Reach for it for thyme, oregano, sage, marjoram. For rosemary, halve it. For basil, mint, parsley, dill, chives — don't substitute at all if you can avoid it; if you must, accept that the dish will taste different.
And always taste before serving. The herb conversions on the reference chart are calibrated against the herbs that survive drying well; the ones above are the exceptions worth remembering.