Replacing 300g High-Hydration (125%) Sourdough Starter with Instant or Active Dry Yeast
Liquid-heavy starter reverse conversion: adding back +166.7g water and +133.3g flour when swapping 300g (125%) starter for yeast.
When removing 300g of 125% hydration sourdough levain from a recipe, add back the 133.3g of flour and 166.7g of water contained inside the levain. In a 450g flour + 315g water sourdough recipe, your restored main dough becomes 583.3g flour and 481.7g water (82.6% True Hydration), leavened with 8.2g (2.6 tsp) of Instant Yeast for a 2-hour rise.
- Add Back Flour
- +133.3gReplaces flour inside 300g (125%) starter
- Add Back Water
- +166.7gReplaces water inside 300g (125%) starter
- Instant Yeast (2-Hr Rise)
- 8.2g (2.6 tsp)For 583.3g total flour batch
- Preserved Hydration
- 82.6%481.7g W / 583.3g F
Sourdough-to-Yeast Conversion Table: 300g at 125% Hydration
The schedule column is the one that changes your timeline: the same starter weight produces a very different ferment at each speed.
| Desired Schedule | IDY Weight | ADY Weight | Fresh Cake Weight | Flour / Water Restoration |
|---|---|---|---|---|
| [Your Batch]: 290g starter at 125% | instant 8.1g | active dry 10.1g | fresh 24.3g | bake 1.5 – 2.0 hours warm bulk rise |
| Scaled Down: 320g starter at 125% | instant 4.1g | active dry 5.2g | fresh 12.4g | bake 3.5 – 4.5 hours slow room-temp rise |
| Scaled Up: 300g starter at 125% | instant 1.5g | active dry 1.8g | fresh 4.4g | bake 12 – 18 hours cold fermentation (39°f / 4°c) |
| Trimmed: 280g starter at 125% | instant 8g | active dry 10.1g | fresh 24.1g | bake 1.5 – 2.0 hours warm bulk rise |
| Expanded: 310g starter at 125% | instant 4.1g | active dry 5.1g | fresh 12.3g | bake 3.5 – 4.5 hours slow room-temp rise |
On-Bench Hydration & Fermentation Adjuster
Modify base flour mass, levain inoculation, or ambient kitchen temperature below to recalculate from this +133.3g baseline.
Why 300g of 125% High-Hydration Starter Requires Asymmetric Water Restoration
The three yeast formats are not interchangeable at equal weight. Active Dry Yeast is a live but partly dehydrated culture carrying roughly 80% of the potency per gram of instant yeast, while fresh compressed cake yeast is only about a third, so 8.2g of instant corresponds to 10.2g of active dry and 24.6g of fresh.
Watch the oven spring rather than the mixing. With 8.2g of commercial yeast the loaf will rise fast in the first 90 minutes, which means less time to develop a rounded shape and more chance of a flat crown if you shape too early.
Step-by-Step Reverse Conversion Protocol (300g @ 125%)
- Restore Base Ingredients (+133.3g F / +166.7g W): Add 133.3g flour and 166.7g water to your main dough (583.3g F / 481.7g W).
- Select Yeast Inoculation by Schedule: Weigh 8.2g (2.6 tsp) Instant Yeast for a 90–120 min rise, or scale down for a 4-hour artisan bulk.
- Mix & Proof Directly: Combine all 583.3g flour, 481.7g water, yeast, and salt without a pre-ferment build.
- Bake on Schedule: Shape once, proof for the remaining time, and bake the moment the dough has doubled rather than waiting for the slow souring a levain would deliver.
Common Scaling & Troubleshooting Questions (+133.3g)
How much flour and water are inside 300g of 125% hydration starter?
300g of 125% hydration sourdough starter contains 133.3g flour and 166.7g water.
What happens to the dough's hydration when I swap out 300g of starter?
Nothing, provided you restore the 133.3g of flour and 166.7g of water inside it. The dough stays at 82.6% true hydration on 583.3g of total flour.
Can I use Active Dry Yeast instead of Instant Yeast to replace 300g starter?
Yes — multiply the 8.2g Instant Yeast weight by 1.25x and dissolve it in warm (100°F / 38°C) water from your 166.7g water addition.