Yeast Conversion Calculator

In short The three commercial yeasts differ in how much water they contain, so a recipe written for one needs converting for another. Fresh yeast is roughly three times the weight of instant, and active dry roughly a third more than instant, which are the working figures this uses. The important thing about them is that they are conventions rather than constants: they vary between manufacturers and between countries, and modern active dry yeasts are often formulated much closer to instant than the traditional ratio implies. If your packet states a conversion, trust it over any table, including this one — it knows what is in it and a general table does not. The practical differences beyond weight matter as much as the arithmetic. Traditional active dry is designed to be rehydrated in warm water before use; instant is milled finer and goes straight into the flour. Many current active dry yeasts work either way, which is exactly why the two categories have blurred and why conversion tables disagree with each other. Fresh yeast is the most perishable by a wide margin — days in a fridge rather than months — and a block that has darkened or dried at the edges has lost strength that no conversion factor accounts for. As a sanity check on any conversion: instant yeast is usually somewhere between 0.5 and 2% of the flour weight. A result far outside that suggests looking again at the original recipe rather than the arithmetic.