How to Replace 4g (1⅓ tsp) Active Dry Yeast with Sourdough Starter in a 500g Flour Recipe
Zero-drift flour and water deduction guide for converting low-yeast (4g active dry yeast) artisan or poolish doughs into 100g sourdough levain.
To replace 4 g of Active Dry Yeast in a 500g flour recipe (at 70% hydration / 350g liquid), use either: (1) Direct yeast equivalency (45.7g of 100% starter, deducting 22.9g flour and 22.9g liquid to leave 477.1g flour and 327.1g water); or (2) Standard 20% artisan inoculation (100g starter, leaving 450g flour and 300g water at 70% True Hydration).
- Direct Yeast Equivalent
- 45.7g StarterDeduct 22.9g flour & 22.9g water
- 20% Artisan Inoculation
- 100g StarterDeduct 50g flour & 50g water
- Adjusted Main Flour/Water
- 450g / 300gPreserves 500g 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 Active Dry Yeast in 500g Flour Across 50% to 125% Starter Hydrations
Compare the packet-equivalency column against the 20% baker's math column to see how much the two conventions diverge on a 500g base.
| Levain Hydration % | Packet Mode Starter & Deductions | Packet Mode Main Mix | 20% Mode Starter & Deductions | 20% Mode Main Mix |
|---|---|---|---|---|
| 100% starter on 500g [Primary] | packet mode 45.7g | main 477.1g / 327.1g | 20% mode 100g | main 450g / 300g |
| 50% starter on 1000g Low Hydration | packet mode 45.7g | main 969.5g / 684.8g | 20% mode 200g | main 866.7g / 633.3g |
| 75% starter on 400g Mid Hydration | packet mode 45.7g | main 373.9g / 260.4g | 20% mode 80g | main 354.3g / 245.7g |
| 125% starter on 500g High Hydration | packet mode 45.7g | main 479.7g / 324.6g | 20% mode 100g | main 455.6g / 294.4g |
| 100% starter on 500g Standard 100% | packet mode 45.7g | main 477.1g / 327.1g | 20% mode 100g | main 450g / 300g |
Dynamic Stoichiometric Workbench (45.7g Starter)
Test custom loaf weights or alternative fermentation schedules directly against the 100g Starter benchmark above.
Replacing Low-Inoculation 4g Active Dry Yeast in 500g Flour Without Shifting Hydration
Scaling the conversion is linear in the flour but not in the yeast. Doubling a 500g base to 1000g while keeping 4g of Active Dry Yeast halves the effective inoculation, so 45.7g of levain is a far gentler ferment than 91.4g would be.
The dough weight of the converted batch is lower than the original. Removing 4g of active dry yeast and adding 45.7g of levain changes the total mass of a 500g flour dough, which is why the finished loaf bakes slightly differently even though the flour and water balance is identical.
3-Step Conversion Checklist (4g Active Dry Yeast → Sourdough in 500g Flour)
- Autolyse First: Combine 450g flour with 300g water (holding back 10% for salt) and rest 45 minutes.
- Add 100g of Ripe Levain: Pinch in the starter, add 2% salt with the reserved water, and mix until the dough is cohesive.
- Four Folds: Space two stretch and folds and two coil folds 30 minutes apart to build gluten without tearing the gas cells.
- Bulk, Shape and Retard: Reach the target rise, shape, and refrigerate 12–16 hours at 38°F before the final bake.
Key Baker's Math Questions (Direct Yeast Equivalent: 45.7g Starter)
How much flour and water do I subtract when adding 100g culture to 500g flour?
At 100% culture hydration, subtract 50g flour and 50g water/milk from your 500g flour recipe (leaving 450g flour and 300g liquid).
What salt level should I use on the converted 500g dough?
Keep 2% of the total system flour, which on a 500g base with 50g of culture flour is about 11g of salt.
What happens to my hydration when I swap 4g active dry commercial yeast for levain?
Nothing, if you deduct correctly. 45.7g of levain carries 22.9g flour and 22.9g water, so removing both keeps the 500g dough at 70% true hydration.