Guides /Baking Science
Yeast conversion.
Fresh, dry, instant.
Fresh yeast, active dry yeast, and instant yeast are not interchangeable 1:1 — here are the exact ratios and the rules for substituting one for another.
Yeast conversion table
| Starting amount | Active dry | Instant / fast-action | Fresh yeast |
|---|---|---|---|
| 1 tsp active dry | 1 tsp | ¾ tsp | ~9 g (⅓ oz) |
| 1 tsp instant | 1¼ tsp | 1 tsp | ~11 g (⅜ oz) |
| 7 g packet active dry | 7 g | 5 g | ~17–20 g |
| 7 g packet instant | 8–9 g | 7 g | ~21 g |
| 25 g fresh yeast | ~10 g | ~8 g | 25 g |
Ratio: instant = 0.75× active dry = 0.33× fresh (by weight)
Instant vs active dry: the key difference
Instant yeast (also sold as "rapid-rise," "quick-rise," or "fast-action" in the UK) has finer granules than active dry yeast and doesn't need to be proofed in warm water before use — it can be added directly to dry ingredients. Active dry yeast benefits from a 5–10 minute proof in 100–110°F / 38–43°C water to verify it's alive and to jump-start the fermentation. Skipping the proof with active dry won't kill the bread, but the rise will be slower and you won't know if the yeast is expired until it's too late.
Fresh yeast (cake yeast)
Fresh yeast is sold in small foil-wrapped blocks and is highly perishable (2–3 weeks refrigerated). It's common in professional bakeries and in European recipes. Fresh yeast is more active than dried, so you need roughly 3× as much by weight when substituting dried for fresh. If a French recipe calls for "25 g levure fraîche," use about 8–9 g instant dry yeast or 10–11 g active dry.
Scaling yeast in large batches
When doubling or tripling a bread recipe, apply the leavening scaling rule: use about 1.75× the yeast for a 2× batch, not exactly 2×. Excess yeast over-ferments, producing too much alcohol and CO₂ — the dough may collapse or develop a sour, yeasty flavour. Alternatively, keep yeast at the original amount and extend the bulk fermentation time by 20–30% to compensate for the larger dough mass taking longer to warm up.
Sourdough and wild yeast
Sourdough starters are a different beast — they're a living culture of wild yeast and bacteria, and their strength varies with the starter's age, hydration, and feeding schedule. There's no fixed conversion from commercial yeast to starter. As a rough guide, replace 1 tsp instant yeast with 100 g of active (recently fed) starter and reduce liquid in the recipe by 50–60 g to account for the starter's hydration.
Refrigerator doughs and cold fermentation
Cold fermentation — mixing a dough and letting it rise slowly in the refrigerator overnight or for up to three days — produces more complex flavour than a same-day rise. For cold fermentation, reduce the yeast amount by 25–50% from the standard recipe quantity. The lower temperature slows yeast activity dramatically, so the smaller amount is enough over the longer time. Instant and active dry yeast both work well for cold fermentation; fresh yeast also works but deteriorates faster than dry.
Checking yeast activity before baking
Active dry yeast (and fresh yeast) should be proofed before use if you're unsure of its freshness: dissolve the yeast in 100–110°F / 38–43°C water with a pinch of sugar and wait 5–10 minutes. Active yeast will foam and bubble noticeably. If nothing happens after 10 minutes, the yeast is dead — discard it and use a fresh packet. Instant yeast can be added directly to dry ingredients and tested simply by observing whether the dough rises during bulk fermentation. If the dough hasn't doubled in size within 2 hours at room temperature, the yeast is likely spent.
Frequently asked questions
- Can I substitute instant yeast for active dry yeast?
- Yes. Use 75% of the active dry amount for instant (e.g. 1 tsp active dry → ¾ tsp instant). Instant yeast can be added directly to dry ingredients; active dry should be proofed in 100–110°F / 38–43°C water for 5–10 minutes first.
- How much fresh yeast equals one packet of active dry yeast?
- One standard 7 g packet of active dry yeast is equivalent to about 17–20 g of fresh yeast.
- Can I substitute active dry yeast for instant yeast?
- Yes — use 125% of the instant amount (e.g. ¾ tsp instant → about 1 tsp active dry). Proof the active dry yeast in warm water first before adding to the recipe.
- How do I scale yeast when doubling a bread recipe?
- Use about 1.75× the yeast for a 2× batch, not exactly 2×. Excess yeast over-ferments, producing too much alcohol and CO₂ — the dough may taste strongly yeasty or collapse. Alternatively, keep yeast at the original amount and extend fermentation time by 20–30%.
- How do I know if my yeast is still active?
- Dissolve the yeast in 100–110°F / 38–43°C water with a pinch of sugar and wait 5–10 minutes. Active yeast will foam visibly. If nothing happens after 10 minutes, the yeast is dead. Instant yeast does not need proofing but can be confirmed active if dough doubles within 2 hours at room temperature.
Scale your bread recipe
Paste your ingredients, set your target scale, and get clean fractions for every line — including yeast amounts.