How to Convert 120g Stiff Sourdough Starter (50% Hydration) to Commercial Yeast
Restoring +80g flour and +40g water when replacing 120g of 50% stiff levain with dry or fresh yeast.
When removing 120g of 50% hydration sourdough starter from a recipe, add back the 80g of flour and 40g of water contained inside the starter. In a 450g flour + 315g water sourdough recipe, your restored main dough becomes 530g flour and 355g water (67% True Hydration), leavened with 7.4g (2.4 tsp) of Instant Yeast for a 2-hour rise.
- Add Back Flour
- +80gReplaces flour inside 120g (50%) starter
- Add Back Water
- +40gReplaces water inside 120g (50%) starter
- Instant Yeast (2-Hr Rise)
- 7.4g (2.4 tsp)For 530g total flour batch
- Preserved Hydration
- 67%355g W / 530g F
Yeast Replacement Matrix for 120g Starter (50% Hydration) Across 3 Fermentation Speeds
Calculated on a 450g main flour + 80g restored starter flour (530g total flour) batch.
| Target Fermentation Schedule | Instant Dry Yeast (IDY) | Active Dry Yeast (ADY) | Fresh Compressed Yeast | Required Dough Restoration |
|---|---|---|---|---|
| Standard Same-Day (1.5–2 hrs) — 140g (50%) [Primary] | IDY 7.6g / 2.5 tsp | ADY 9.5g / 3.1 tsp | fresh 22.8g | restore 93.3g + 46.7g |
| Slow Artisan Bulk (3.5–4.5 hrs) — 120g (50%) Compact Read | IDY 3.7g / 1.2 tsp | ADY 4.6g / 1.5 tsp | fresh 11.1g | restore 80g + 40g |
| Overnight No-Knead / Cold Proof (12–18 hrs) — 100g (50%) Extended Read | IDY 1.3g / 0.4 tsp | ADY 1.6g / 0.5 tsp | fresh 3.9g | restore 66.7g + 33.3g |
| Standard Same-Day (1.5–2 hrs) — 130g (50%) Generous Read | IDY 7.5g / 2.4 tsp | ADY 9.4g / 3 tsp | fresh 22.5g | restore 86.7g + 43.3g |
| Slow Artisan Bulk (3.5–4.5 hrs) — 110g (50%) Lean Read | IDY 3.7g / 1.2 tsp | ADY 4.6g / 1.5 tsp | fresh 11g | restore 73.3g + 36.7g |
Live Parameter Solver for How to Convert 120g Stiff Sourdough Starte
Dial in custom baker's percentages and export your adjusted +80g formula for bake day.
Decomposing 120g of 50% Stiff Levain: High-Flour Mass Conservation
Water temperature becomes more critical once wild yeast is out of the equation. Commercial Saccharomyces cerevisiae tolerates a wider range than a mixed levain culture, but a direct 7.4g dose still prefers water around 100°F (38°C) for a 1.5 – 2.0 hours warm bulk rise.
Punching down, shaping and retarding are the stages that a levain dough was really buying you. Removing the starter removes that work, so plan the 1.5 – 2.0 hours warm bulk rise as a single continuous bulk and shape only once, at the end.
Step-by-Step Reverse Conversion Protocol (120g @ 50%)
- Use a Scale, Not a Spoon: 7.4g of instant yeast is 2.4 teaspoons, and a kitchen teaspoon of yeast varies by up to 20% between brands, so weighing is the only accurate approach.
- Combine Everything at Once: 530g flour, 355g water at 100°F (38°C), 7.4g yeast and 2% salt.
- Knead to Windowpane: A commercial-yeast dough develops gluten faster, so stop as soon as the gluten film is smooth and you will avoid tearing it.
- Proof and Bake: Allow 1.5 – 2.0 hours warm bulk rise, shape once, and bake the moment the volume has roughly doubled.
Cereal Chemistry & Bench Execution FAQs
How much grain and water are inside 120g of 50% hydration starter?
120g of 50% hydration sourdough starter contains 80g grain and 40g water.
Can I convert a dough that also contains a poolish or preferment?
Yes, but count the preferment's yeast separately and subtract it from the 7.4g, otherwise the 530g dough will over-proof.
Can I scale the conversion to a different flour weight?
Yes. The yeast dose is a percentage of total flour, so on a larger batch multiply 7.4g by the ratio of the new flour weight to 530g.