Converting High-Yeast 9g (1 tbsp / 3 tsp) Instant Dry Yeast to Sourdough Levain in 500g Flour
High-inoculation conversion math comparing 128.6g direct yeast equivalency vs. 100g (20% baker's math) for 500g flour recipes.
Converting 500g flour and 350g water from 9g Instant Dry Yeast to 100% hydration levain requires deducting starter mass so 70% True Total Hydration holds steady: weigh 100g starter with 450g main flour and 300g liquid (20% mode) or 128.6g starter with 435.7g flour and 285.7g liquid (packet mode).
- Direct Yeast Equivalent
- 128.6g StarterDeduct 64.3g flour & 64.3g 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
Yeast-to-Sourdough Conversion Table: 9g Instant Dry Yeast on a 500g Base
Rows recompute the full conversion independently, so the flour, liquid and starter columns always reconcile.
| Starter Hydration | Packet-Equivalent Starter (Deductions) | Adjusted Main Dough (Packet Mode) | 20% Artisan Starter (Deductions) | Adjusted Main Dough (20% Mode) |
|---|---|---|---|---|
| Line 500g at 75% [Baseline] | packet 128.6g (deduct 73.5g/55.1g) | remaining 426.5g + 294.9g | artisan 100g (deduct 57.1g/42.9g) | remaining 442.9g + 307.1g |
| Line 1000g at 100% Stiffer Starter | packet 128.6g (deduct 64.3g/64.3g) | remaining 935.7g + 635.7g | artisan 200g (deduct 100g/100g) | remaining 900g + 600g |
| Line 400g at 125% Wetter Starter | packet 128.6g (deduct 57.1g/71.4g) | remaining 342.9g + 208.6g | artisan 80g (deduct 35.6g/44.4g) | remaining 364.4g + 235.6g |
| Line 500g at 50% Lighter Starter | packet 128.6g (deduct 85.7g/42.9g) | remaining 414.3g + 307.1g | artisan 100g (deduct 66.7g/33.3g) | remaining 433.3g + 316.7g |
| Line 500g at 100% Heavier Starter | packet 128.6g (deduct 64.3g/64.3g) | remaining 435.7g + 285.7g | artisan 100g (deduct 50g/50g) | remaining 450g + 300g |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this 128.6g Starter baseline.
Balancing Osmotic Stress & Hydration When Replacing 9g Instant Dry Yeast in 500g Flour
Commercial instant dry yeast (9g) introduces negligible moisture to a 500g flour mix, whereas 100g of 100% hydration levain carries 50g fermented flour and 50g water. Deducting those exact weights keeps the 500g system at 70% hydration.
A hybrid is often the best answer in practice: use 128.6g of levain to preserve the flavour of the original 9g dose, but plan the schedule as if you were using 100g at 20% inoculation, because the acid load and the fermentation time both follow the latter.
3-Step Conversion Checklist (9g Instant Dry Yeast → Sourdough in 500g Flour)
- Check the Starter Is Ripe: 100g of levain must be domed, bubbly and at full stretch; a flat starter slows the 4.0 – 5.5 hours at 76°F (24°C) window significantly.
- Combine 500g of Flour with the Adjusted Liquid: Pour 300g, saving 10% to dissolve the salt later.
- Fold in 100g Starter and 2% Salt: Add the levain, pinch through the dough, and work in the salt water.
- Ferment to +50%: Judge by volume in a straight-sided jar, then shape, retard overnight and bake on a preheated stone or in a Dutch oven.
Common Scaling & Troubleshooting Questions (128.6g Starter)
How much flour and water do I subtract when adding 100g starter to 500g flour?
At 100% starter hydration, subtract 50g flour and 50g water/milk from your 500g flour recipe (leaving 450g flour and 300g liquid).
Should I use 128.6g or 100g of starter?
Use 128.6g if you want to preserve the exact leavening power of 9g instant dry yeast. Use 100g if you want standard 20% artisan inoculation regardless of the original yeast weight.
Is a 500g sourdough conversion suitable for a pizza or focaccia base?
Yes, and long cold retarding is often an advantage for pizza. Mix 100g of levain into 450g flour and 300g water and refrigerate 24–48 hours.