Instant and active dry yeast swap 1:1 by weight or volume (King Arthur); active dry just rises a little slower. For fresh yeast, use one-third as much dry yeast by weight.
Ratios from university extension services and King Arthur Baking. Checked .
Yeast (instant, active dry, fresh) substitutes, best first
- For 1 packet (1/4 oz, about 2 1/4 tsp) active dry yeastSame amount instant yeastBest for: all yeast breads
King Arthur: 1:1 by weight or volume; neither needs proofing. Active dry rises a bit slower—add 15-20 minutes to a 1-hour rise.
- For Fresh (compressed) yeastDry yeast weighing 1/3 as much (e.g. 15 g fresh = 5 g dry)Best for: converting European recipes
King Arthur: multiply fresh by 0.33.
- For 1 cake (0.6 oz) compressed yeast1 packet (1/4 oz) active dry yeast, or 2 1/4 tspBest for: classic recipes
Nebraska; UC says a scant 2 1/2 tsp, Colorado State 2 1/2 tsp.
What not to use
Chemical leaveners (baking powder or soda) don't make yeast bread; the dough won't develop the same rise or flavor.
Why the swaps work
Yeast ferments sugars into carbon dioxide and flavor compounds. Instant and active dry are both dried yeasts that work the same by weight (active dry starts a little slower); fresh yeast is moist, so it takes about three times the weight for the same rise.
Questions people ask
Do I need to proof active dry yeast?
Not usually; King Arthur says modern active dry can be mixed in dry, though you can proof it.
How much yeast is in a packet?
A packet is 1/4 oz (about 7 g), roughly 2 1/4 tsp.
How do I convert fresh yeast to instant?
Multiply the fresh weight by 0.33.