How to Convert 300g Stiff Sourdough Starter (50% Hydration) to Commercial Yeast
Restoring +200g flour and +100g water when replacing 300g of 50% stiff levain with dry or fresh yeast.
Why bother converting back at all? Three reasons. You need a predictable two-hour rise for a schedule; you want the cleaner flavour of a commercial-yeast crumb; or you have 300g of levain in the jar you would rather not waste. The cost is that you lose the acid complexity, so season the dough with the recipe's own aromatics.
- Add Back Flour
- +200gReplaces flour inside 300g (50%) starter
- Add Back Water
- +100gReplaces water inside 300g (50%) starter
- Instant Yeast (2-Hr Rise)
- 9.1g (2.9 tsp)For 650g total flour batch
- Preserved Hydration
- 63.8%415g W / 650g F
Sourdough-to-Yeast Conversion Table: 300g at 50% Hydration
The restoration column shows the flour and water that must go back into the main mix to keep the 63.8% hydration intact.
| Proofing Plan | Instant Dry Yeast | Active Dry Yeast | Fresh Compressed Yeast | Dough Restoration |
|---|---|---|---|---|
| [Primary]: 300g starter at 50% | instant 9.1g | active dry 11.4g | fresh 27.3g | bake 1.5 – 2.0 hours warm bulk rise |
| Compact Read: 310g starter at 50% | instant 4.6g | active dry 5.7g | fresh 13.8g | bake 3.5 – 4.5 hours slow room-temp rise |
| Extended Read: 290g starter at 50% | instant 1.6g | active dry 2g | fresh 4.8g | bake 12 – 18 hours cold fermentation (39°f / 4°c) |
| Generous Read: 320g starter at 50% | instant 9.3g | active dry 11.6g | fresh 27.9g | bake 1.5 – 2.0 hours warm bulk rise |
| Lean Read: 280g starter at 50% | instant 4.5g | active dry 5.6g | fresh 13.4g | bake 3.5 – 4.5 hours slow room-temp rise |
Custom Batch Recalculation Engine
Fine-tune starter hydration between 50% stiff and 125% liquid while keeping your sourdough → yeast reverse conversion ratios locked.
Decomposing 300g of 50% Stiff Levain: High-Flour Mass Conservation
A cold overnight ferment changes the yeast arithmetic entirely. The 9.1g 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 650g of flour.
Keep the salt. A 2% salt dough is the reference point for commercial-yeast baking, and a converted 650g dough has the same total flour as the original, so the original salt weight transfers across unchanged.
Step-by-Step Reverse Conversion Protocol (300g @ 50%)
- Weigh the Restoration (200g + 100g): Set out the flour and water that were hiding inside the 300g of 50% starter before you do anything else.
- Build the Dough (650g F / 415g W): Combine them with the original 450g and 315g, then add 2% salt and 9.1g 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.
Technical Q&A: How to Convert 300g Stiff Sourdough Starter (50%
Can I use fresh cake yeast instead of dry yeast for the 300g starter swap?
Yes, but fresh compressed yeast is only about a third as potent per gram, so you need roughly 27.3g instead of 9.1g.
Does the converted dough keep the same dough weight?
Almost — the 300g of starter is replaced by the 9.1g of yeast plus the 200g of flour and 100g of water you put back, which is a slightly different total.
Will my converted dough taste different from the levain version?
Yes. The roughly 6g of residual acid inside 300g of starter was providing both flavour and tenderising, and commercial yeast replaces neither.