Swapping one yeast for another
Recipes are written for the yeast the author had on hand. A European bread book calls for fresh yeast, an American one for a packet of active dry, and a bread machine manual for instant yeast. All three are the same organism, Saccharomyces cerevisiae, but they hold different amounts of water and living cells, so the weights are not interchangeable. This calculator converts between them by weight and gives teaspoons and packets for the dry types.
The conversion ratios
The usual baking ratios, by weight, are:
- Fresh (cake) yeast = 1
- Active dry yeast = 0.4 of the fresh weight
- Instant yeast = about 0.33 of the fresh weight
In other words, 1 g of instant yeast does the work of about 3 g of fresh yeast, and 1 g of active dry yeast replaces 2.5 g of fresh yeast. Instant yeast is about 20 percent stronger than active dry, which is why many bakers use a quarter less of it.
Worked example: one packet of active dry yeast
A US packet holds 1/4 oz, about 7 g or 2 1/4 teaspoons.
- Fresh equivalent: 7 × 2.5 = 17.5 g of fresh yeast.
- Instant equivalent: 17.5 ÷ 3 = 5.8 g, a little under 2 teaspoons.
- With 500 g of flour (about 4 cups), the fresh-yeast rate is 17.5 ÷ 500 = 3.5%, a normal level for a home loaf that rises in one to two hours.
Equivalents at a glance
| Active dry | Fresh | Instant |
|---|---|---|
| 1/2 packet (3.5 g) | 8.8 g | 2.9 g |
| 1 packet (7 g) | 17.5 g | 5.8 g |
| 2 packets (14 g) | 35 g | 11.7 g |
| 3 packets (21 g) | 52.5 g | 17.5 g |
How to use each type
- Fresh yeast comes in moist cakes, keeps about two weeks in the refrigerator and is crumbled into the flour or dissolved in lukewarm water. It can be frozen, though it loses some strength.
- Active dry yeast has larger granules and is traditionally dissolved in warm water (about 105 to 110 °F) for 5 to 10 minutes before mixing. Modern active dry yeast can also be mixed in directly if the dough is given a little more time.
- Instant yeast has finer granules and goes straight into the dry ingredients. It is the type sold for bread machines and “rapid rise”, which may contain additives that speed the first rise.
Tips for a reliable rise
- Test old yeast. Stir a teaspoon of yeast and a pinch of sugar into warm water. If it does not foam within 10 minutes, replace it.
- Do not overheat. Water above about 130 °F kills yeast.
- Adjust for time, not only for type. Halving the yeast and letting the dough rise longer in the refrigerator gives more flavor. The calculator shows the yeast as a share of the flour so you can compare recipes.
- Salt and sugar slow yeast down. Very rich doughs such as brioche use more yeast for that reason.