How to Convert 180g Stiff Sourdough Starter (75% Hydration) to Commercial Yeast
Restoring +102.9g flour and +77.1g water when replacing 180g of 75% stiff levain with dry or fresh yeast.
A 75% hydration levain is roughly 57% flour and 43% water by weight, so 180g of it hides 102.9g of flour and 77.1g of water. Deleting it without restoring both shrinks the loaf and skews the ratio away from 70.9%. Restoring them and dosing 7.7g of yeast keeps the dough identical.
- Add Back Flour
- +102.9gReplaces flour inside 180g (75%) starter
- Add Back Water
- +77.1gReplaces water inside 180g (75%) starter
- Instant Yeast (2-Hr Rise)
- 7.7g (2.5 tsp)For 552.9g total flour batch
- Preserved Hydration
- 70.9%392.1g W / 552.9g F
Sourdough-to-Yeast Conversion Table: 180g at 75% Hydration
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 |
|---|---|---|---|---|
| [Anchor]: 180g starter at 75% | instant 7.7g | active dry 9.7g | fresh 23.2g | bake 1.5 – 2.0 hours warm bulk rise |
| One Step Down: 190g starter at 75% | instant 3.9g | active dry 4.9g | fresh 11.7g | bake 3.5 – 4.5 hours slow room-temp rise |
| One Step Up: 170g starter at 75% | instant 1.4g | active dry 1.7g | fresh 4.1g | bake 12 – 18 hours cold fermentation (39°f / 4°c) |
| Two Steps Down: 200g starter at 75% | instant 7.9g | active dry 9.9g | fresh 23.7g | bake 1.5 – 2.0 hours warm bulk rise |
| Two Steps Up: 160g starter at 75% | instant 3.8g | active dry 4.7g | fresh 11.4g | 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 180g of 75% Stiff Levain: High-Flour Mass Conservation
A cold overnight ferment changes the yeast arithmetic entirely. The 7.7g that produces a 1.5 – 2.0 hours warm bulk rise would be a violent over-proof at 39°F (4°C), so the overnight schedule needs roughly a fifth of the instant-yeast dose for the same 552.9g of grain.
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 (180g @ 75%)
- Weigh the Restoration (102.9g + 77.1g): Set out the flour and water that were hiding inside the 180g of 75% starter before you do anything else.
- Build the Dough (552.9g F / 392.1g W): Combine them with the original 450g and 315g, then add 2% salt and 7.7g 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.
Frequently Asked Questions for This Sourdough → Yeast Reverse Conversion Spec
What happens to the dough's hydration when I swap out 180g of starter?
Nothing, provided you restore the 102.9g of flour and 77.1g of water inside it. The dough stays at 70.9% true hydration on 552.9g of total flour.
Can I convert a stiff 50% levain to yeast?
Yes, and the deduction is larger on the flour side: 180 grams at 50% hydration holds 120g flour and 60g water rather than the 102.9g / 77.1g of a 75% starter.
Does converting to yeast change the fermentation time?
Dramatically. A levain dough on this 552.9g base would need many hours; the 7.7g of commercial yeast gives you a 1.5 – 2.0 hours warm bulk rise.