Why the ratios are what they are
Fresh yeast is about 70% water; drying removes that water and concentrates the living cells. Active dry yeast keeps some protective coating around the cells, which is why it must be rehydrated before use; instant yeast is dried finer and mixed with dough conditioners, so it activates on contact with liquid in the dough. The practical result is the standard conversion: fresh 100%, active dry 40%, instant 33% by weight.
| Fresh yeast | Active dry yeast | Instant yeast |
|---|---|---|
| 10 g | 4 g | 3.3 g |
| 15 g | 6 g | 5 g |
| 20 g | 8 g | 6.7 g |
| 25 g | 10 g | 8.3 g |
| 30 g | 12 g | 10 g |
| 50 g | 20 g | 16.7 g |
How each type is used
Fresh yeast crumbles straight into the dough or dissolves in a little of the recipe's liquid — never in liquid hotter than about 45°C, which kills it. Active dry yeast needs proofing: dissolve it in warm water (40–46°C) with a pinch of sugar and wait 5–10 minutes until it foams; if it does not foam, the yeast is dead and the dough will not rise. Instant yeast skips all of this — mix it with the flour, add the liquid, and knead. The one exception is very dry or very cold doughs, where even instant yeast benefits from a brief soak.
The volume trap
Many charts convert yeast in teaspoons, but that is unreliable: a teaspoon of instant yeast weighs about 3.1 g for one brand and 3.6 g for another, and active dry granules are larger and lighter per spoon. Two teaspoons of “the same” yeast from different jars can differ by 20%. Weighing in grams removes the brand, the granule size and the spoon from the equation entirely.
Adjusting rise times after a swap
Converted correctly, all three yeasts raise the same dough — but not on the same schedule. Fresh yeast starts fastest and suits short, warm rises. Active dry lags by 15–30 minutes on the first rise while it rehydrates; give it that time rather than adding more yeast. Instant yeast rises fast and tolerates a cooler dough, which makes it the best choice for overnight fridge rises. In every case, judge the dough by whether it has doubled, not by the clock: temperature moves rise times more than yeast type does.
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