Swapping fresh herbs for dried (or vice versa) is one of the most common recipe substitutions, and getting the ratio wrong can throw off a dish's flavor balance. This calculator applies the standard 3:1 fresh-to-dried substitution ratio used by professional and home cooks alike, so you can confidently adjust any recipe.
How the 3:1 ratio works
Drying an herb removes most of its water content, which concentrates the remaining essential oils and flavor compounds. As a rule of thumb, dried herbs are about three times more potent by volume than fresh herbs of the same type. That means 3 parts fresh herb is roughly equivalent to 1 part dried herb — so to substitute dried for fresh, divide the fresh amount by 3; to substitute fresh for dried, multiply the dried amount by 3.
This 3:1 guideline comes from long-standing culinary convention (it appears in classic reference texts like the Culinary Institute of America's professional cooking guides) rather than a single scientific study, but it holds up well across most common cooking herbs.
Inputs and what they mean
Enter the amount your recipe specifies, choose the unit (teaspoon, tablespoon, or cup — the calculator keeps the same unit on both sides of the conversion), and pick the direction: Fresh → Dried when you have a fresh-herb amount and need the dried equivalent, or Dried → Fresh for the reverse. The result updates instantly as you type.
Limits and edge cases
The 3:1 ratio is a solid general-purpose default, but it is not universal. Woody, resinous herbs like rosemary and thyme retain much more of their oil content when dried, so many cooks use closer to a 1:1 or 2:1 ratio for those — see the Common Herbs tab for specifics. Ground spices are more concentrated still than dried leaf herbs and typically need an even bigger reduction than 3:1 (closer to 4:1 or higher). And dried herbs lose potency the longer they sit in storage, so a jar that's a year or two old may need more than the standard ratio suggests to hit the same flavor intensity. When in doubt, start with slightly less dried herb than the ratio recommends — you can always add more, but you can't take it back out.