How to Convert Between Fresh, Active Dry, and Instant Yeast

Fresh yeast is moist yeast sold in blocks; it has a high water content, so the greatest weight is needed. Active dry yeast is dried and granulated; it is typically rehydrated in warm water before use. Instant yeast is ground more finely and can be mixed directly into flour. All three do the same job; only their concentrations differ, so the amount must be converted when switching between them in a recipe. Instant yeast is the most commonly available type in stores, so converting the amounts of fresh yeast in older recipes is a common need.

The practical ratio to remember is 3:1:0.8. To convert fresh yeast to active dry yeast, divide the amount by three; to convert dry yeast to fresh, multiply by three. Instant yeast is roughly four-fifths the amount of active dry yeast: use 8 grams of instant yeast in place of 10 grams of active dry yeast. For example, a recipe calling for 15 grams of fresh yeast for 500 grams of flour can be made with 5 grams of active dry yeast or 4 grams of instant yeast, with a similar result.

Conversion involves more than the amount; the method of use also changes. Dissolve fresh yeast by crumbling it into warm water. Let active dry yeast stand in warm water with a pinch of sugar for 5 to 10 minutes; if no foam forms on the surface, the yeast is dead and the dough must be started over. Instant yeast is mixed directly into the flour and needs no pre-treatment. For all three types, avoid direct contact with salt: add the salt to the flour and the yeast in a separate spot, then combine them when mixing begins.

The ratio is a starting point, not an exact equation. Yeast strength varies by brand, production date, and storage conditions; a package of active dry yeast opened months ago may not raise dough as well as a fresh one. So watch the dough during the first attempt: if it rises later than expected, increase the ratio slightly in the next batch. Sourdough is not included in this comparison because its strength depends entirely on its own maturity. Because of this same uncertainty, always measure yeast with a precise scale, never with cups or spoons.

Storage also affects conversion. Fresh yeast is kept in the refrigerator and has a short shelf life; it can be frozen, but its strength decreases somewhat after thawing. Active dry and instant yeast keep for a long time in unopened packages; after opening, keep them in a sealed container in the refrigerator. Regardless of the type, do not let the dough’s water exceed 50°C / 122°F; that temperature kills the yeast and the dough will not rise. Once thawed, frozen fresh yeast should not be left standing; use it that day.