Fresh vs active dry vs instant yeast
One organism in three formats, and a ratio worth memorising.
They are the same species in three formats. The usual ratio is 1 instant = 1.25 active dry = 3 fresh. A 7 g packet of instant equals 21 g of fresh yeast.
Conversion table
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| If the recipe calls for | Fresh | Active dry | Instant |
|---|---|---|---|
| One standard packet | 21 g | 8.75 g | 7 g |
| Half a 42 g block | 21 g | 8.75 g | 7 g |
| For 500 g flour (1 %) | 15 g | 6.25 g | 5 g |
| For 1 kg flour (1 %) | 30 g | 12.5 g | 10 g |
| 25 g of fresh yeast | 25 g | 10.4 g | 8.3 g |
The three formats
Fresh (compressed) yeast
A moist, crumbly block sold refrigerated. It is largely water, which is why you need three times the weight. It keeps badly: two or three weeks in the fridge. Dissolve it in warm liquid before use; many bakers prefer its aroma.
Active dry yeast
Larger dehydrated granules. Traditionally rehydrated in warm water with a pinch of sugar for a few minutes before use. Keeps for months in the cupboard and over a year refrigerated.
Instant dry yeast
A finer granule with a higher concentration of live cells. It goes straight into the flour without rehydrating, which makes it the most convenient. It is what comes in 7 g sachets.
Which one to use
- Starting out, instant: fewer steps, fewer things to go wrong.
- Baking often, fresh is worth it for the aroma, if you use it before it turns.
- Keeping some in the cupboard, dry: it lasts months.
Less yeast is almost always better
Using less yeast and giving the dough more time produces better flavour: it develops more aroma and is easier to digest. A dough at 0.5 % instant yeast fermenting overnight in the fridge makes clearly better bread than one at 2 % in two hours.
Sources and methodology
The 3 : 1.25 : 1 ratio is the reference commonly used by manufacturers and bakers. It is not a physical constant: real activity depends on brand, freshness and dough temperature.
Frequently asked questions
How much dry yeast equals 25 g of fresh?
About 8.3 g of instant or 10.4 g of active dry, using the 3 : 1.25 : 1 ratio.
How much fresh yeast is one packet of dry?
A 7 g packet of instant equals about 21 g of fresh yeast, half a 42 g block.
Does instant yeast need rehydrating?
No: mix it straight into the flour. Active dry is usually rehydrated in warm liquid first.
Can they be substituted for each other?
Yes, adjusting the amount with the ratio. What changes is how you incorporate it and, slightly, the fermentation time.
How much yeast goes into bread?
0.5 to 2 % of the flour weight as instant yeast, depending on how long you want the fermentation to take. Less yeast and more time tastes better.