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Yeast conversion calculator

The three forms of baker’s yeast differ in water content and viability, so they are not interchangeable gram for gram.

degrees C
As fresh yeast
10.00g
= Exact Yeast conversion
As active dry yeast
4.00
As instant yeast
3.33
Fermentation rate against 24 degrees C
1.000
Relative proving time
1.000
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  1. Amount you have = 10
  2. Type you have = 1
  3. Dough temperature = 24
  4. As fresh yeast = 10 * 1 = 10
  5. As active dry yeast = 10 / 2.5 = 4
  6. As instant yeast = 10 / 3 = 3.333 33
  7. Fermentation rate against 24 degrees C = 2^((24 - 24) / 8) = 1
  8. Relative proving time = 1 > 0 ? 1/1 : 0 = 1

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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    The formula

    • fresh : active dry : instant is roughly 3 : 1.2 : 1 by weight
    • fermentation rate roughly doubles for every 8 degrees Celsius of dough temperature

    Active dry yeast traditionally needs rehydrating in warm water; instant yeast can go straight into the flour.

    The temperature rule is a rough Q10-style approximation and breaks down above about 35 degrees, where the yeast starts to suffer.

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