Convert 7g (1 Packet / 2¼ tsp) Active Dry Yeast to Sourdough Starter (400g Flour Recipe)
Zero-drift flour and liquid deduction math for converting 7g of active dry yeast into 50%–125% hydration sourdough levain on a 400g base.
Start with the mass balance. 7g of active dry yeast contributes no flour and no water to your dough; 80g of 100% hydration starter contributes 40g of each. So a 400g flour, 280g liquid formula becomes 360g flour and 240g liquid once the levain goes in, and the dough will ferment on sourdough's clock rather than yeast's.
- Direct Yeast Equivalent
- 80g StarterDeduct 40g flour & 40g 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
Starter Deduction Grid for 7g (1 Packet / 2¼ tsp) Active Dry Yeast in 400g Flour
Every figure is derived from the 400g flour / 280g liquid base formula and the 7g active dry yeast dose.
| Starter Hydration Level | Levain Required by Yeast Weight | Flour & Liquid Left in the Bowl | Levain Required at 20% Inoculation | Corrected Main Mix |
|---|---|---|---|---|
| 50% starter on 400g [Your Formula] | packet mode 80g | main 346.7g / 253.3g | 20% mode 80g | main 346.7g / 253.3g |
| 100% starter on 400g Leaner Dough | packet mode 80g | main 360g / 240g | 20% mode 80g | main 360g / 240g |
| 125% starter on 500g Wetter Dough | packet mode 80g | main 464.4g / 305.6g | 20% mode 100g | main 455.6g / 294.4g |
| 75% starter on 1000g Tighter Dough | packet mode 80g | main 954.3g / 665.7g | 20% mode 200g | main 885.7g / 614.3g |
| 100% starter on 400g Looser Dough | packet mode 80g | main 360g / 240g | 20% mode 80g | main 360g / 240g |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this 80g Starter baseline.
Why 7g Active Dry Yeast Cannot Be Swapped in 400g Flour Without Deducting Starter Water
Hydration drift is the most common way this conversion goes wrong. Adding 80g of levain to 400g flour and 280g water without the 40g deduction pushes the dough to 72.7% true hydration, and the extra free water is exactly what turns a slack dough into a puddle.
Temperature expectations change too. Because a 400g levain dough ferments more slowly, the bulk window shifts, and bakers who keep the old 76°F target often find their 80g starter version over-proofing in a warm kitchen where the commercial version never had time to over-proof.
3-Step Conversion Checklist (7g Active Dry Yeast → Sourdough in 400g Flour)
- Weigh Active Levain (80g or 80g): Measure 80g peaked 100% starter for 20% inoculation, or 80g for direct 7g Active Dry Yeast equivalency.
- Deduct Main Flour & Liquid (400g Base): Scale main flour to 360g (-40g) and liquid to 240g (-40g).
- Ferment for 4.0 – 5.5 hours at 76°F (24°C): Hold the 400g dough at 75°F–78°F until +50% volumetric expansion before shaping and cold proofing.
- Retard and Bake: Cold-proof the shaped dough for 12–16 hours at 38°F, then bake covered and uncover to a deep mahogany crust.
Common Scaling & Troubleshooting Questions (80g Starter)
How do I convert a sweet or enriched recipe with 7 g of Active Dry Yeast?
The flour and water deduction is identical, but reduce the sugar by about 10%–15%, because the 4.0 – 5.5 hours at 76°F (24°C) sourdough ferment converts more of it than a two-hour commercial rise.
Can I convert a 400g dough that already contains a preferment or poolish?
Yes, but dissolve the preferment's yeast into the main mix first so the full 7 grams of leavening power is counted. Then deduct 40g flour and 40g water for the levain you are adding.
How much longer does sourdough take to rise than 7g of Active Dry Yeast?
Expect bulk fermentation on a 400g grain batch to take 4.0 – 5.5 hours at 76°F (24°C), roughly 3 to 4 times longer than commercial active dry yeast.