Convert 5g (1⅔ tsp) Fresh Cake Yeast to Sourdough Starter (500g Flour Recipe)
Zero-drift flour and liquid deduction math for converting 5g of fresh cake yeast into 50%–125% hydration sourdough levain on a 500g base.
There are two defensible answers to this conversion, and the difference matters. Packet-equivalency treats 5g of Fresh Cake Yeast as a fixed quantity of leavening power, so you need 23.8g of ripe starter and must remove 11.9g grain plus 11.9g water from the 500g base. Baker's math instead standardises on 20% inoculation, giving 100g of starter on the same 500g grain with 450g grain and 300g liquid left in the bowl.
- Direct Yeast Equivalent
- 23.8g StarterDeduct 11.9g flour & 11.9g 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
Starter Deduction Grid for 5g (1⅔ tsp) Fresh Cake Yeast in 500g Flour
Every figure is derived from the 500g flour / 350g liquid base formula and the 5g fresh cake yeast dose.
| Starter Hydration Level | Levain Required by Yeast Weight | Flour & Liquid Left in the Bowl | Levain Required at 20% Inoculation | Corrected Main Mix |
|---|---|---|---|---|
| 400g flour @ 75% [Primary] | 23.8g starter (13.6g F / 10.2g W) | 386.4g F / 269.8g W | 80g starter (45.7g F / 34.3g W) | 354.3g F / 245.7g W |
| 500g flour @ 100% Low Hydration | 23.8g starter (11.9g F / 11.9g W) | 488.1g F / 338.1g W | 100g starter (50g F / 50g W) | 450g F / 300g W |
| 500g flour @ 125% Mid Hydration | 23.8g starter (10.6g F / 13.2g W) | 489.4g F / 336.8g W | 100g starter (44.4g F / 55.6g W) | 455.6g F / 294.4g W |
| 1000g flour @ 50% High Hydration | 23.8g starter (15.9g F / 7.9g W) | 984.1g F / 692.1g W | 200g starter (133.3g F / 66.7g W) | 866.7g F / 633.3g W |
| 500g flour @ 100% Standard 100% | 23.8g starter (11.9g F / 11.9g W) | 488.1g F / 338.1g W | 100g starter (50g F / 50g W) | 450g F / 300g W |
Interactive Yeast ↔ Sourdough Conversion Calculator
Compare your exact mixing bowl dimensions, flour protein percentage, or discard weight in real time.
Why 5g Fresh Cake Yeast Cannot Be Swapped in 500g Flour Without Deducting Starter Water
Because fresh cake commercial yeast is a pure monoculture of Saccharomyces cerevisiae, transitioning your 500g batch to sourdough requires tracking volumetric aliquot rise (+50%) over 4.0 – 5.5 hours at 76°F (24°C) rather than watching a 60-minute clock.
The dough weight of the converted batch is lower than the original. Removing 5 grams of fresh cake yeast and adding 23.8g of levain changes the total mass of a 500g flour dough, which is why the finished loaf bakes slightly differently even though the flour and water balance is identical.
3-Step Conversion Checklist (5g Fresh Cake Yeast → Sourdough in 500g Flour)
- Calculate the Deduction First: 23.8g of starter carries 11.9g of flour and 11.9g of water, so write those two numbers on your bench sheet before you open the flour bag.
- Build the 500g Base: Use 488.1g flour and 338.1g liquid, which keeps the dough at 70% true hydration.
- Incorporate 23.8g of Starter: Dimple in the levain and 2% salt, mix to full cohesion, and rest 30 minutes before the first fold.
- Watch the Aliquot, Not the Clock: Ferment at 75°F until a 30g sample reaches +50% volume, which on sourdough is far more reliable than a timer.
Frequently Asked Questions for This Yeast ↔ Sourdough Conversion Spec
Can I halve the recipe and still use 5g of Fresh Cake Yeast?
You can, but the effective inoculation doubles, so 23.8g of levain on half the grain ferments faster than the original. Plan for a shorter bulk.
Does the type of commercial yeast change the starter weight?
Yes. Fresh Cake Yeast has its own potency per gram, so 5 grams of it converts to 23.8g of levain rather than the 100g that the 20% rule would prescribe on a 500g base.
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).