How to Replace 4g (1⅓ tsp) Instant Dry Yeast with Sourdough Starter in a 400g Flour Recipe
Zero-drift flour and water deduction guide for converting low-yeast (4g instant dry yeast) artisan or poolish doughs into 80g sourdough levain.
Start with the mass balance. 4g of instant dry yeast contributes no grain and no water to your dough; 57.1g of 100% hydration starter contributes 28.6g of each. So a 400g grain, 280g liquid formula becomes 371.4g grain and 251.4g liquid once the levain goes in, and the dough will ferment on sourdough's clock rather than yeast's.
- Direct Yeast Equivalent
- 57.1g StarterDeduct 28.6g flour & 28.6g 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
Replacing 4g Instant Dry Yeast in 400g Flour Across 50% to 125% Starter Hydrations
Every figure is derived from the 400g flour / 280g liquid base formula and the 4g instant dry yeast dose.
| Levain Hydration % | Packet Mode Starter & Deductions | Packet Mode Main Mix | 20% Mode Starter & Deductions | 20% Mode Main Mix |
|---|---|---|---|---|
| [Exact Target]: 500g / 50% | hidden 38.1g F + 19g W | → 461.9g / 331g | hidden 66.7g F + 33.3g W | → 433.3g / 316.7g |
| Alt Row A: 1000g / 100% | hidden 28.6g F + 28.6g W | → 971.4g / 671.4g | hidden 100g F + 100g W | → 900g / 600g |
| Alt Row B: 400g / 125% | hidden 25.4g F + 31.7g W | → 374.6g / 248.3g | hidden 35.6g F + 44.4g W | → 364.4g / 235.6g |
| Alt Row C: 400g / 75% | hidden 32.7g F + 24.5g W | → 367.3g / 255.5g | hidden 45.7g F + 34.3g W | → 354.3g / 245.7g |
| Alt Row D: 400g / 100% | hidden 28.6g F + 28.6g W | → 371.4g / 251.4g | hidden 40g F + 40g W | → 360g / 240g |
Interactive Yeast ↔ Sourdough Conversion Calculator
Compare your exact mixing bowl dimensions, flour protein percentage, or discard weight in real time.
Replacing Low-Inoculation 4g Instant Dry Yeast in 400g Flour Without Shifting Hydration
Scaling the conversion is linear in the flour but not in the yeast. Doubling a 400g base to 800g while keeping 4g of Instant Dry Yeast halves the effective inoculation, so 57.1g of levain is a far gentler ferment than 114.2g would be.
If your original recipe used 4 g of instant dry yeast for a sweet or enriched dough, the 57.1g levain version usually needs its sugar reduced slightly, because the longer fermentation converts more of it and the finished crumb sweetens on its own.
3-Step Conversion Checklist (4g Instant Dry Yeast → Sourdough in 400g Flour)
- Calculate the Deduction First: 57.1g of starter carries 28.6g of flour and 28.6g of water, so write those two numbers on your bench sheet before you open the flour bag.
- Build the 400g Base: Use 371.4g flour and 251.4g liquid, which keeps the dough at 70% true hydration.
- Incorporate 57.1g of Starter: Dimple in the sourdough culture and 2% salt, mix to full cohesion, and rest 30 minutes before the first fold.
- Watch the Aliquot, Not the Clock: Ferment at 75°F until a 30g sample reaches +50% volume, which on sourdough is far more reliable than a timer.
Frequently Asked Questions for This Yeast ↔ Sourdough Conversion Spec
What salt level should I use on the converted 400g dough?
Keep 2% of the total system flour, which on a 400g base with 40g of culture flour is about 8.8g of salt.
What happens to my hydration when I swap 4g instant dry commercial yeast for levain?
Nothing, if you deduct correctly. 57.1g of levain carries 28.6g flour and 28.6g water, so removing both keeps the 400g dough at 70% true hydration.
Does converting to sourdough change the dough weight?
Yes, slightly. The 400g flour and 280g liquid original carried 4g of dry yeast; the sourdough culture version carries 57.1g of starter instead, so expect a small shift in finished loaf weight.