How to Convert 100g Stiff Sourdough Starter (75% Hydration) to Commercial Yeast
Restoring +57.1g flour and +42.9g water when replacing 100g of 75% stiff levain with dry or fresh yeast.
A 75% hydration starter is roughly 57% grain and 43% water by weight, so 100g of it hides 57.1g of grain and 42.9g of water. Deleting it without restoring both shrinks the loaf and skews the ratio away from 70.6%. Restoring them and dosing 7.1g of yeast keeps the dough identical.
- Add Back Flour
- +57.1gReplaces flour inside 100g (75%) starter
- Add Back Water
- +42.9gReplaces water inside 100g (75%) starter
- Instant Yeast (2-Hr Rise)
- 7.1g (2.3 tsp)For 507.1g total flour batch
- Preserved Hydration
- 70.6%357.9g W / 507.1g F
Gram Weights for Replacing 100g of 75% Hydration Starter
The three yeast formats differ in potency per gram, which is why the Instant column is the baseline the other two are scaled from.
| Target Rise Schedule | IDY Dose | ADY Dose | Fresh Cake Dose | Restoration Required |
|---|---|---|---|---|
| Line 100g / 75% [Anchor] | 7.1g IDY (2.3 tsp) | 8.9g ADY (2.9 tsp) | 21.3g cake yeast | 1.5 – 2.0 hours warm bulk rise |
| Line 110g / 75% One Step Down | 3.6g IDY (1.2 tsp) | 4.5g ADY (1.4 tsp) | 10.8g cake yeast | 3.5 – 4.5 hours slow room-temp rise |
| Line 90g / 75% One Step Up | 1.3g IDY (0.4 tsp) | 1.6g ADY (0.5 tsp) | 3.8g cake yeast | 12 – 18 hours cold fermentation (39°F / 4°C) |
| Line 120g / 75% Two Steps Down | 7.3g IDY (2.3 tsp) | 9.1g ADY (2.9 tsp) | 21.8g cake yeast | 1.5 – 2.0 hours warm bulk rise |
| Line 80g / 75% Two Steps Up | 3.5g IDY (1.1 tsp) | 4.3g ADY (1.4 tsp) | 10.4g cake yeast | 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 +57.1g baseline.
Decomposing 100g of 75% Stiff Levain: High-Flour Mass Conservation
Salt interacts with the change. A levain dough was usually formulated for a 2% salt dough, and swapping in 7.1g of commercial yeast on the same 507.1g of grain keeps that salt level, which is a sensible place to leave the formula alone.
Watch the oven spring rather than the mixing. With 7.1g 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 (100g @ 75%)
- Use a Scale, Not a Spoon: 7.1g of instant yeast is 2.3 teaspoons, and a kitchen teaspoon of yeast varies by up to 20% between brands, so weighing is the only accurate approach.
- Combine Everything at Once: 507.1g flour, 357.9g water at 100°F (38°C), 7.1g yeast and 2% salt.
- Knead to Windowpane: A commercial-yeast dough develops gluten faster, so stop as soon as the gluten film is smooth and you will avoid tearing it.
- Proof and Bake: Allow 1.5 – 2.0 hours warm bulk rise, shape once, and bake the moment the volume has roughly doubled.
Common Scaling & Troubleshooting Questions (+57.1g)
Is 100g of 75% starter easier to replace than a wetter starter?
Easier in one sense: a stiffer starter carries more flour and less water per gram, so the 57.1g / 42.9g restoration is larger on the flour side and smaller on the water side.
What happens to the dough's hydration when I swap out 100 g of starter?
Nothing, provided you restore the 57.1g of flour and 42.9g of water inside it. The dough stays at 70.6% true hydration on 507.1g of total flour.
Can I scale the conversion to a different flour weight?
Yes. The yeast dose is a percentage of total flour, so on a larger batch multiply 7.1g by the ratio of the new flour weight to 507.1g.