How to Convert 120g Stiff Sourdough Starter (75% Hydration) to Commercial Yeast
Restoring +68.6g flour and +51.4g water when replacing 120g of 75% stiff levain with dry or fresh yeast.
Converting 120 g of 75% starter to yeast in one line: restore 68.6g of flour and 51.4g of water to the main dough, yielding 518.6g of flour and 366.4g of liquid at 70.7% true hydration, then dose 7.3g (2.3 tsp) of instant yeast for a 1.5 – 2.0 hours warm bulk rise.
- Add Back Flour
- +68.6gReplaces flour inside 120g (75%) starter
- Add Back Water
- +51.4gReplaces water inside 120g (75%) starter
- Instant Yeast (2-Hr Rise)
- 7.3g (2.3 tsp)For 518.6g total flour batch
- Preserved Hydration
- 70.7%366.4g W / 518.6g F
Reverse Conversion Chart: 120g Starter → Commercial Yeast
The schedule column is the one that changes your timeline: the same starter weight produces a very different ferment at each speed.
| Desired Schedule | IDY Weight | ADY Weight | Fresh Cake Weight | Flour / Water Restoration |
|---|---|---|---|---|
| [Exact Target]: 110g starter at 75% | instant 7.2g | active dry 9g | fresh 21.5g | bake 1.5 – 2.0 hours warm bulk rise |
| Alt Row A: 140g starter at 75% | instant 3.7g | active dry 4.6g | fresh 11.1g | bake 3.5 – 4.5 hours slow room-temp rise |
| Alt Row B: 120g starter at 75% | instant 1.3g | active dry 1.6g | fresh 3.9g | bake 12 – 18 hours cold fermentation (39°f / 4°c) |
| Alt Row C: 100g starter at 75% | instant 7.1g | active dry 8.9g | fresh 21.3g | bake 1.5 – 2.0 hours warm bulk rise |
| Alt Row D: 130g starter at 75% | instant 3.7g | active dry 4.6g | fresh 11g | bake 3.5 – 4.5 hours slow room-temp rise |
Interactive Sourdough → Yeast Reverse Conversion Calculator
Compare your exact mixing bowl dimensions, flour protein percentage, or discard weight in real time.
Decomposing 120g of 75% Stiff Levain: High-Flour Mass Conservation
Salt interacts with the change. A levain dough was usually formulated for a 2% salt dough, and swapping in 7.3g of commercial yeast on the same 518.6g of flour keeps that salt level, which is a sensible place to leave the formula alone.
Crust colour is a tell. A levain dough browns more slowly because its sugars are already partly consumed, so a converted dough reaches a deeper, faster colour at the same temperature and often benefits from a slightly cooler oven.
Step-by-Step Reverse Conversion Protocol (120g @ 75%)
- Audit the Original Formula: Confirm the recipe's yeast was the only leavening, and that the 120g of 75% starter was the sole source of the 68.6g of hidden flour.
- Rebuild at Full Scale: The dough is now 518.6g flour and 366.4g liquid — the same numbers as before, minus the starter.
- Dose for the Schedule You Want: 7.3g (2.3 tsp) of instant yeast for a 1.5 – 2.0 hours warm bulk rise; use about a fifth of that for a cold overnight ferment.
- Bake and Compare: The crumb will be lighter and less acid-forward, but the volume and crust colour should be close to the levain original.
Frequently Asked Questions for This Sourdough → Yeast Reverse Conversion Spec
How long should the converted dough bulk for at room temperature?
Plan on 1.5 – 2.0 hours warm bulk rise, then shape and bake immediately. There is no levain to justify a long slow bulk, and a commercial-yeast dough left longer simply over-proofs.
Does converting to yeast change the fermentation time?
Dramatically. A levain dough on this 518.6g base would need many hours; the 7.3g of commercial yeast gives you a 1.5 – 2.0 hours warm bulk rise.
How much flour and water are inside 120g of 75% hydration starter?
120g of 75% hydration sourdough starter contains 68.6g flour and 51.4g water.