Recipes assume you're using whatever yeast the author had in their pantry — usually active dry, instant, or fresh (cake) yeast — and these three types aren't interchangeable 1:1. This calculator converts between them using the standard baking-industry substitution ratios, so a recipe written for one type still rises correctly with another.
How the Yeast Converter works
The calculator routes every conversion through an active-dry-yeast equivalent. Active dry is the baseline (factor 1), instant yeast is 0.75× as much by weight (it's more concentrated, so recipes use less), and fresh yeast is 2× as much by weight (it's less concentrated and contains more moisture). Converting an amount first back to its active-dry equivalent, then forward to the target type, guarantees a fresh-to-instant or fresh-to-fresh swap never silently applies a ratio twice.
Inputs and what they mean
Enter the amount you have (or the recipe calls for) and the unit it's measured in — teaspoon, tablespoon, gram, or packet. One standard US packet is 2¼ teaspoons, or about 7 grams, which is the assumption baked into the unit conversion. Then pick the yeast type you're converting from and the type you're converting to; the result updates as soon as either changes.
Limits and edge cases
These are standard industry approximations, not exact chemistry — actual yeast potency varies slightly by brand and age, and old or improperly stored yeast performs below these ratios regardless of type. Fresh (cake) yeast has a short refrigerated shelf life (about two weeks) and should be proofed visually before a big bake even though it doesn't need a warm-water proof. For sourdough starter substitutions, which follow a different hydration-based ratio rather than a fixed weight multiplier, use a dedicated sourdough conversion resource instead of this calculator.