If a recipe gives fresh yeast and you have dry yeast, do not replace it gram for gram. Read the dry yeast label first, because the correct conversion belongs to the product—not to the words “fresh” and “dry” alone.
For Saf-instant, the manufacturer says to use one third of the pressed-yeast weight. Red Star's own chart gives a different result: one 2 oz / 56.7 g cake equals three 7 g packets of its dry yeast. Both are valid instructions for those products, and that is exactly why I would not publish one universal conversion table.
The quantities I would use
These examples do the arithmetic from each manufacturer's stated equivalence. Choose the row that matches the yeast in your hand; do not average the two columns.
- 30 g fresh yeast → 10 g Saf-instant, using Saf-instant's 3:1 pressed-to-instant ratio.
- 20 g fresh yeast → 6.7 g Saf-instant, using the same Saf-instant ratio.
- 30 g fresh yeast → about 11.1 g Red Star dry yeast, from Red Star's 56.7 g fresh = 21 g dry chart.
- 20 g fresh yeast → about 7.4 g Red Star dry yeast, from the same Red Star chart.
A worked brioche example
My brioche formula uses 20 g fresh yeast with 500 g flour and 75 g sugar. The sugar is 15% of the flour weight.
If the substitute is Saf-instant Gold, the manufacturer's 3:1 ratio gives 20 ÷ 3 = 6.7 g. Gold is the relevant Saf product here because its technical sheet is written for sweet dough containing at least 5% sugar by flour weight. I would mix it directly with the flour or add it at the start of kneading, as Saf instructs, and keep it away from ice or iced water.
If the substitute is Red Star active dry or instant yeast, Red Star's chart gives about 7.4 g for 20 g fresh yeast. Red Star says its active dry and instant products can replace each other one for one in traditional hand or mixer methods, although instant may rise faster.
I have not presented either dry-yeast amount as Tanya's tested replacement for this brioche. They are manufacturer-backed starting quantities. The first batch still needs its dough temperature, bulk fermentation and final proof recorded.
How to calculate another weight
Round only as far as your scale can measure reliably. For a small batch, a scale reading to 0.1 g is more useful than converting the answer to teaspoons.
- Saf-instant example: fresh yeast ÷ 3 = Saf-instant weight.
- Red Star example: fresh yeast × 21 ÷ 56.7 = Red Star dry yeast weight.
- For another brand or a specialised yeast, use that manufacturer's conversion rather than borrowing either calculation.
Active dry and instant are not universal categories
Some conversion charts treat active dry and instant yeast differently. Red Star does not for traditional dough mixing: its current guidance permits a one-for-one substitution by weight for its own products and tells the baker to expect instant yeast to work faster.
That does not turn every active dry yeast into every instant yeast. Follow the packet's mixing method as well as its dose. If the label asks for rehydration, take that liquid from the formula total. If the label says to add the yeast directly, do that.
For enriched dough, choose the product before the ratio
Sugar makes yeast selection more important. In the Saf-instant range, Red is described for dough with 0–10% sugar by flour weight, while Gold is recommended from 5% upward. The ranges overlap, so the number is a product guide, not a universal boundary between ordinary and osmotolerant yeast.
For brioche, calculate sugar as a percentage of flour before choosing the dry yeast. A formula with 75 g sugar and 500 g flour is 15% sugar, so Saf's own guidance points to Gold. If your product uses another range or another threshold, follow that specification.
Do not force the old proofing time
A correct weight conversion does not guarantee the same clock. Yeast condition, product type, dough temperature, sugar, fat, salt and mixing all change fermentation speed.
After a substitution, I would keep the rest of the formula unchanged, record the finished dough temperature and judge the dough by expansion and strength. If it starts slowly, check the product method and dough temperature before adding more yeast.
What I would keep unchanged in the first test
Changing the yeast, hydration and proofing temperature together makes the result impossible to read. Change the yeast product and its instructed mixing method first; then adjust one variable only if the recorded batch shows a real need.
- Flour, liquid, sugar, salt, eggs and butter.
- Mixer, mixing sequence and target dough temperature.
- Container size and fermentation temperature.
- The visual and tactile end points for bulk fermentation and final proof.
Why gram-for-gram replacement fails
Fresh compressed yeast contains far more water than dry yeast. Dry yeast is concentrated, so 20 g dry yeast in place of 20 g fresh would be a substantial overdose under both manufacturer systems above.
The small amount of water removed with fresh yeast is usually less important than the activity difference in a home-size batch. In a tightly controlled production formula, review total water after the first comparable test rather than changing it by guesswork.
If the dough is slow after conversion
- Confirm that the yeast type and amount match the same manufacturer's instructions.
- Check the use-by date and storage history.
- Measure the dough temperature, not only the room temperature.
- Check whether an active dry product required rehydration.
- Check the sugar-to-flour percentage and whether the product is intended for sweet dough.
- Give the dough time to show fermentation before increasing the dose.
The decision in one line
Use the yeast manufacturer's own ratio and method, then let the dough decide the schedule. For the 20 g fresh yeast in my brioche formula, that means 6.7 g Saf-instant Gold by Saf's guidance or about 7.4 g Red Star dry yeast by Red Star's chart—not one invented number for every packet on the shelf.