Converting High-Yeast 9g (1 tbsp / 3 tsp) Active Dry Yeast to Sourdough Levain in 400g Flour
High-inoculation conversion math comparing 102.9g direct yeast equivalency vs. 80g (20% baker's math) for 400g flour recipes.
None of the arithmetic changes with the yeast brand, but the type does: active dry yeast carries its own potency per gram, so 9g of it converts to 102.9g of culture rather than the 80g that 20% baker's math prescribes. Either way, deduct the hidden flour and water — 51.4g and 51.4g in packet mode — or the 400g dough will not hold 70% hydration.
- Direct Yeast Equivalent
- 102.9g StarterDeduct 51.4g flour & 51.4g water
- 20% Artisan Inoculation
- 80g StarterDeduct 40g flour & 40g water
- Adjusted Main Flour/Water
- 360g / 240gPreserves 400g total system flour at 20% levain
- Sourdough Bulk Window
- 4.0 – 5.5 hoursAt 76°F (24°C) vs. 1–1.5 hrs for commercial yeast
Hidden Flour & Water Inside the Levain (9g Active Dry Yeast → 400g dough)
Starter hydration shifts the deduction asymmetrically: a stiffer levain carries more flour and less water per gram.
| Hydration of Levain | Yeast-Equivalent Starter | Remaining Main Formula | Baker's-Math Starter | Remaining Main Formula |
|---|---|---|---|---|
| Case 400g @ 100% [Your Formula] | 102.9g levain | subtract 51.4g flour, 51.4g water | 80g levain | subtract 40g flour, 40g water |
| Case 400g @ 50% Leaner Dough | 102.9g levain | subtract 68.6g flour, 34.3g water | 80g levain | subtract 53.3g flour, 26.7g water |
| Case 500g @ 75% Wetter Dough | 102.9g levain | subtract 58.8g flour, 44.1g water | 100g levain | subtract 57.1g flour, 42.9g water |
| Case 1000g @ 125% Tighter Dough | 102.9g levain | subtract 45.7g flour, 57.1g water | 200g levain | subtract 88.9g flour, 111.1g water |
| Case 400g @ 100% Looser Dough | 102.9g levain | subtract 51.4g flour, 51.4g water | 80g levain | subtract 40g flour, 40g water |
Dynamic Stoichiometric Workbench (102.9g Starter)
Test custom loaf weights or alternative fermentation schedules directly against the 80g Starter benchmark above.
Balancing Osmotic Stress & Hydration When Replacing 9g Active Dry Yeast in 400g Flour
Hydration drift is the most common way this conversion goes wrong. Adding 102.9g of sourdough culture to 400g flour and 280g water without the 51.4g deduction pushes the dough to 73.4% true hydration, and the extra free water is exactly what turns a slack dough into a puddle.
Direct packet scaling of 9g (1 tbsp / 3 tsp) Active Dry Yeast maps to 102.9g starter (-51.4g flour / -51.4g water), while artisan baker's math standardises inoculation at 20% of 400g (80g starter, leaving 360g main flour and 240g liquid).
3-Step Conversion Checklist (9g Active Dry Yeast → Sourdough in 400g Flour)
- Scale the Recipe Sheet: Rewrite the original 400g, 280g, 9 g active dry yeast formula as 360g flour, 240g liquid, 80g levain and 2% salt.
- Hydrate the Flour: Mix the adjusted flour and 90% of the liquid and rest 45 minutes to fully hydrate the starch.
- Add Levain, Salt and the Last 10%: Work in 80g of starter, 2% salt and the reserved water, then complete the gluten with 3 coil folds.
- Ferment, Shape, Retard: Let the 400g dough reach +50% volume, shape tightly, cold-proof 12–16 hours and bake at 450°F for a blistered crust.
Key Baker's Math Questions (Direct Yeast Equivalent: 102.9g Starter)
What salt level should I use on the converted 400g dough?
Keep 2% of the total system grain, which on a 400g base with 40g of starter grain is about 8.8g of salt.
Is a 400g sourdough conversion suitable for a pizza or focaccia base?
Yes, and long cold retarding is often an advantage for pizza. Mix 80g of levain into 360g flour and 240g water and refrigerate 24–48 hours.
Does converting to sourdough change the dough weight?
Yes, slightly. The 400g flour and 280g liquid original carried 9g of dry yeast; the levain version carries 102.9g of starter instead, so expect a small shift in finished loaf weight.