Converting High-Yeast 9g (1 tbsp / 3 tsp) Instant Dry Yeast to Sourdough Levain in 1000g Flour
High-inoculation conversion math comparing 128.6g direct yeast equivalency vs. 200g (20% baker's math) for 1000g flour recipes.
If your goal is simply a sourdough version of a 1000g recipe that used 9g of Instant Dry Yeast, the simplest path is 20% inoculation: 200g of ripe levain, with 100g grain and 100g water removed from the main mix, leaving 900g and 600g. Expect 4.0 – 5.5 hours at 76°F (24°C) instead of a two-hour rise.
- Direct Yeast Equivalent
- 128.6g StarterDeduct 64.3g flour & 64.3g water
- 20% Artisan Inoculation
- 200g StarterDeduct 100g flour & 100g water
- Adjusted Main Flour/Water
- 900g / 600gPreserves 1000g 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 9g (1 tbsp / 3 tsp) Instant Dry Yeast in 1000g Flour
Compare the packet-equivalency column against the 20% baker's math column to see how much the two conventions diverge on a 1000g base.
| Starter Hydration Level | Levain Required by Yeast Weight | Flour & Liquid Left in the Bowl | Levain Required at 20% Inoculation | Corrected Main Mix |
|---|---|---|---|---|
| [Exact Target]: 400g / 75% | hidden 73.5g F + 55.1g W | → 326.5g / 224.9g | hidden 45.7g F + 34.3g W | → 354.3g / 245.7g |
| Alt Row A: 1000g / 100% | hidden 64.3g F + 64.3g W | → 935.7g / 635.7g | hidden 100g F + 100g W | → 900g / 600g |
| Alt Row B: 500g / 125% | hidden 57.1g F + 71.4g W | → 442.9g / 278.6g | hidden 44.4g F + 55.6g W | → 455.6g / 294.4g |
| Alt Row C: 1000g / 50% | hidden 85.7g F + 42.9g W | → 914.3g / 657.1g | hidden 133.3g F + 66.7g W | → 866.7g / 633.3g |
| Alt Row D: 1000g / 100% | hidden 64.3g F + 64.3g W | → 935.7g / 635.7g | hidden 100g F + 100g W | → 900g / 600g |
Dynamic Stoichiometric Workbench (128.6g Starter)
Test custom loaf weights or alternative fermentation schedules directly against the 200g Starter benchmark above.
Balancing Osmotic Stress & Hydration When Replacing 9g Instant Dry Yeast in 1000g Flour
Flour mass moves too, and bakers tend to forget it. The 64.3g of pre-fermented flour inside 128.6g of levain means the true total flour of your dough is not 1000g but 1064.3g once the starter is added, which is what makes 70% the correct target rather than the naive 70%.
Judge the conversion on the dough, not on the scale. The dough should feel the same slackness it had with the original 9g of instant dry yeast, dome predictably, and hold its shape at shaping. If it is spreading, the 64.3g of hidden starter water was not deducted.
3-Step Conversion Checklist (9g Instant Dry Yeast → Sourdough in 1000g Flour)
- Autolyse First: Combine 900g flour with 600g water (holding back 10% for salt) and rest 45 minutes.
- Add 200g 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: 128.6g Starter)
Does the type of commercial yeast change the starter weight?
Yes. Instant Dry Yeast has its own potency per gram, so 9g of it converts to 128.6g of levain rather than the 200g that the 20% rule would prescribe on a 1000g base.
Will my 1000g sourdough version rise the same way as the 9g instant dry yeast original?
No. Sourdough produces gas more slowly and with different gas retention, so judge the converted dough by +50% volumetric rise in a straight-sided jar rather than by doubling in a bowl.
Does converting to sourdough change the dough weight?
Yes, slightly. The 1000g flour and 700g liquid original carried 9g of dry yeast; the levain version carries 128.6g of culture instead, so expect a small shift in finished loaf weight.