Replacing 50g High-Hydration (125%) Sourdough Starter with Instant or Active Dry Yeast
Liquid-heavy starter reverse conversion: adding back +27.8g water and +22.2g flour when swapping 50g (125%) starter for yeast.
When removing 50 g of 125% hydration sourdough starter from a recipe, add back the 22.2g of flour and 27.8g of water contained inside the starter. In a 450 g flour + 315g water sourdough recipe, your restored main dough becomes 472.2g flour and 342.8g water (72.6% True Hydration), leavened with 6.6g (2.1 tsp) of Instant Yeast for a 2-hour rise.
- Add Back Flour
- +22.2gReplaces flour inside 50g (125%) starter
- Add Back Water
- +27.8gReplaces water inside 50g (125%) starter
- Instant Yeast (2-Hr Rise)
- 6.6g (2.1 tsp)For 472.2g total flour batch
- Preserved Hydration
- 72.6%342.8g W / 472.2g F
Three Fermentation Schedules for a 50g (125%) Starter Swap
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 |
|---|---|---|---|---|
| Standard Same-Day (1.5–2 hrs) — 50g (125%) [Anchor] | IDY 6.6g / 2.1 tsp | ADY 8.3g / 2.7 tsp | fresh 19.8g | restore 22.2g + 27.8g |
| Slow Artisan Bulk (3.5–4.5 hrs) — 40g (125%) One Step Down | IDY 3.3g / 1.1 tsp | ADY 4.1g / 1.3 tsp | fresh 9.8g | restore 17.8g + 22.2g |
| Overnight No-Knead / Cold Proof (12–18 hrs) — 60g (125%) One Step Up | IDY 1.2g / 0.4 tsp | ADY 1.5g / 0.5 tsp | fresh 3.6g | restore 26.7g + 33.3g |
| Standard Same-Day (1.5–2 hrs) — 30g (125%) Two Steps Down | IDY 6.5g / 2.1 tsp | ADY 8.1g / 2.6 tsp | fresh 19.5g | restore 13.3g + 16.7g |
| Slow Artisan Bulk (3.5–4.5 hrs) — 70g (125%) Two Steps Up | IDY 3.4g / 1.1 tsp | ADY 4.2g / 1.4 tsp | fresh 10.1g | restore 31.1g + 38.9g |
Interactive Sourdough → Yeast Reverse Conversion Calculator
Compare your exact mixing bowl dimensions, flour protein percentage, or discard weight in real time.
Why 50g of 125% High-Hydration Starter Requires Asymmetric Water Restoration
Salt interacts with the change. A levain dough was usually formulated for a 2% salt dough, and swapping in 6.6g of commercial yeast on the same 472.2g of flour keeps that salt level, which is a sensible place to leave the formula alone.
The acid-free dough behaves differently in the mixer. Commercial yeast raises gas faster, so the dough will feel more elastic earlier and needs less mechanical work; over-mixing is the most common failure in a converted batch.
Step-by-Step Reverse Conversion Protocol (50g @ 125%)
- Plan Around the Lost Complexity: Without a levain you lose the slow acid build, so if the 50g of 125% starter was there for flavour, add a little honey or malt and a spoonful of yoghurt.
- Restore the Mass: Return 22.2g of flour and 27.8g of water to the base recipe.
- Dose the Yeast: 6.6g (2.1 tsp) of instant, 8.3g of active dry, or 19.8g of fresh cake yeast.
- Ferment, Shape, Bake: Respect the 1.5 – 2.0 hours warm bulk rise schedule, and remember the 72.6% hydration is unchanged by the swap.
Frequently Asked Questions for This Sourdough → Yeast Reverse Conversion Spec
Does the converted batch keep the same batch weight?
Almost — the 50g of starter is replaced by the 6.6g of yeast plus the 22.2g of flour and 27.8g of water you put back, which is a slightly different total.
Can I use fresh cake yeast instead of dry yeast for the 50g starter swap?
Yes, but fresh compressed yeast is only about a third as potent per gram, so you need roughly 19.8g instead of 6.6g.
Can I use Active Dry Yeast instead of Instant Yeast to replace 50g starter?
Yes — multiply the 6.6g Instant Yeast weight by 1.25x and dissolve it in warm (100°F / 38°C) water from your 27.8g water addition.