The quick rule
Dry yeast is concentrated, so you need less of it than fresh (cake) yeast:
- Active dry = half the weight of fresh yeast.
- Instant (rapid-rise, bread machine) = one third of the weight of fresh yeast.
- A US yeast packet holds ¼ oz: 7 g, or 2¼ teaspoons.
| Fresh (cake) | Active dry | Instant | Flour (approx.) |
|---|---|---|---|
| 21 g (¾ oz) | 10.5 g | 7 g (1 packet · 2¼ tsp) | 3½–4 cups |
| 15 g | 7.5 g | 5 g (1¾ tsp) | 2½–3 cups |
| 10 g | 5 g | 3.5 g (1¼ tsp) | 1½–2 cups |
Guideline amounts for breads with a 1–2 hour rise. Long cold rises in the fridge use much less.
How to use each one
- Fresh (cake): crumble and dissolve it in a little lukewarm water or milk. It keeps about 2 weeks in the fridge.
- Active dry: granules that should be proofed in lukewarm liquid for 5–10 minutes before adding.
- Instant: fine granules you mix straight into the flour. The easiest to use.
The liquid should be lukewarm, not hot: above about 115 °F (45 °C) yeast starts to die.
What about baking powder?
Baking powder and baking soda are not yeast: they are chemical leaveners that make cakes and muffins rise in the oven. They won’t work for bread or pizza dough, and yeast won’t work in a cake batter.