Convert 80g Sourdough Starter (100% Hydration) to Commercial Yeast
How to remove 80g of 100% hydration levain from any sourdough recipe by restoring +40g flour and +40g water.
Think of the swap as a bookkeeping exercise, not a recipe change. 80g of 100% starter is not 80g of nothing — it is 40g of flour and 40g of water that you are about to delete. Put them back, and the dough returns to 490g flour and 355g water at 72.4% hydration, now leavened by 6.9g of instant yeast for a 1.5 – 2.0 hours warm bulk rise.
- Add Back Flour
- +40gReplaces flour inside 80g (100%) starter
- Add Back Water
- +40gReplaces water inside 80g (100%) starter
- Instant Yeast (2-Hr Rise)
- 6.9g (2.2 tsp)For 490g total flour batch
- Preserved Hydration
- 72.4%355g W / 490g F
Three Fermentation Schedules for a 80g (100%) Starter Swap
The restoration column shows the flour and water that must go back into the main mix to keep the 72.4% hydration intact.
| Proofing Plan | Instant Dry Yeast | Active Dry Yeast | Fresh Compressed Yeast | Dough Restoration |
|---|---|---|---|---|
| Line 80g / 100% [Baseline] | 6.9g IDY (2.2 tsp) | 8.6g ADY (2.8 tsp) | 20.6g cake yeast | 1.5 – 2.0 hours warm bulk rise |
| Line 70g / 100% Smaller Batch | 3.4g IDY (1.1 tsp) | 4.2g ADY (1.4 tsp) | 10.2g cake yeast | 3.5 – 4.5 hours slow room-temp rise |
| Line 90g / 100% Larger Batch | 1.2g IDY (0.4 tsp) | 1.5g ADY (0.5 tsp) | 3.7g cake yeast | 12 – 18 hours cold fermentation (39°F / 4°C) |
| Line 60g / 100% Half Size | 6.7g IDY (2.2 tsp) | 8.4g ADY (2.7 tsp) | 20.2g cake yeast | 1.5 – 2.0 hours warm bulk rise |
| Line 100g / 100% Double Size | 3.5g IDY (1.1 tsp) | 4.4g ADY (1.4 tsp) | 10.5g cake yeast | 3.5 – 4.5 hours slow room-temp rise |
Interactive Sourdough → Yeast Reverse Conversion Calculator
Compare your exact mixing bowl dimensions, flour protein percentage, or discard weight in real time.
Decomposing 80g of 100% Hydration Starter: Flour + Water Conservation
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 6.9g of instant corresponds to 8.6g of active dry and 20.7g of fresh.
Watch the oven spring rather than the mixing. With 6.9g 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 (80g @ 100%)
- Use a Scale, Not a Spoon: 6.9g of instant yeast is 2.2 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: 490g flour, 355g water at 100°F (38°C), 6.9g 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.
Frequently Asked Questions for This Sourdough → Yeast Reverse Conversion Spec
Can I use Active Dry Yeast instead of Instant Yeast to replace 80g starter?
Yes — multiply the 6.9g Instant Yeast weight by 1.25x and dissolve it in warm (100°F / 38°C) water from your 40g water addition.
How much instant yeast replaces 80g of 100% sourdough starter?
For a standard 1.5–2 hour rise on a 490g total flour loaf, use 6.9g (2.2 tsp) of Instant Dry Yeast and add back 40g flour + 40g water.
Will my converted dough taste different from the levain version?
Yes. The roughly 2g of residual acid inside 80g of starter was providing both flavour and tenderising, and commercial yeast replaces neither.