Convert 120g Sourdough Starter (100% Hydration) to Commercial Yeast
How to remove 120g of 100% hydration levain from any sourdough recipe by restoring +60g flour and +60g water.
Replacing 120g of 100% hydration levain with commercial yeast requires restoring +60g dry flour and +60g water so batch mass and 73.5% True Hydration stay unchanged (510g total flour / 375g total water on a 450g base), paired with 7.1g (2.3 tsp) Instant Dry Yeast.
- Add Back Flour
- +60gReplaces flour inside 120g (100%) starter
- Add Back Water
- +60gReplaces water inside 120g (100%) starter
- Instant Yeast (2-Hr Rise)
- 7.1g (2.3 tsp)For 510g total flour batch
- Preserved Hydration
- 73.5%375g W / 510g F
Reverse Conversion Chart: 120g Starter → Commercial Yeast
The restoration column shows the flour and water that must go back into the main mix to keep the 73.5% hydration intact.
| Proofing Plan | Instant Dry Yeast | Active Dry Yeast | Fresh Compressed Yeast | Dough Restoration |
|---|---|---|---|---|
| 100g 100% starter — Standard Same-Day (1.5–2 hrs) [Your Batch] | use 7g instant | use 8.8g active dry | use 21g fresh | add 50g flour + 50g water |
| 120g 100% starter — Slow Artisan Bulk (3.5–4.5 hrs) Scaled Down | use 3.6g instant | use 4.5g active dry | use 10.7g fresh | add 60g flour + 60g water |
| 140g 100% starter — Overnight No-Knead / Cold Proof (12–18 hrs) Scaled Up | use 1.3g instant | use 1.6g active dry | use 3.9g fresh | add 70g flour + 70g water |
| 110g 100% starter — Standard Same-Day (1.5–2 hrs) Trimmed | use 7.1g instant | use 8.8g active dry | use 21.2g fresh | add 55g flour + 55g water |
| 130g 100% starter — Slow Artisan Bulk (3.5–4.5 hrs) Expanded | use 3.6g instant | use 4.5g active dry | use 10.8g fresh | add 65g flour + 65g water |
Real-Time Dough & Starter Scaling Sandbox
Scale this Convert 120g Sourdough Starter (100% specification up or down on your digital scale with zero hydration drift.
Decomposing 120g of 100% Hydration Starter: Flour + Water Conservation
The three yeast formats are not interchangeable at equal weight. Active Dry Yeast is a live but partly dehydrated culture carrying roughly 80% of the potency per gram of instant yeast, while fresh compressed cake yeast is only about a third, so 7.1g of instant corresponds to 8.9g of active dry and 21.3g of fresh.
A practical test of a successful conversion: the dough should feel smooth rather than tacky after mixing, hold a windowpane, and reach the same volume in the oven as the original levain dough even though it got there in a fraction of the time.
Step-by-Step Reverse Conversion Protocol (120g @ 100%)
- Weigh the Restoration (60g + 60g): Set out the flour and water that were hiding inside the 120g of 100% starter before you do anything else.
- Build the Dough (510g F / 375g W): Combine them with the original 450g and 315g, then add 2% salt and 7.1g of instant yeast.
- Mix and Rest: Knead to a smooth, cohesive dough and rest 10 minutes before a second mix to develop gluten.
- Proof for 1.5 – 2.0 hours warm bulk rise: Bulk at 78°F (26°C) until doubled, then shape, pan and bake immediately.
Diagnostic Answers: Convert 120g Sourdough Starter (100% Hydrati
Can I use fresh cake yeast instead of dry yeast for the 120g starter swap?
Yes, but fresh compressed yeast is only about a third as potent per gram, so you need roughly 21.3g instead of 7.1g.
Does converting to yeast change the fermentation time?
Dramatically. A levain dough on this 510g base would need many hours; the 7.1g of commercial yeast gives you a 1.5 – 2.0 hours warm bulk rise.
Does the converted dough keep the same dough weight?
Almost — the 120g of starter is replaced by the 7.1g of yeast plus the 60g of flour and 60g of water you put back, which is a slightly different total.