Every sourdough recipe you have ever baked is secretly four numbers: flour (always 100%), water, salt, and starter — each written as a percentage of the flour weight. Learn the convention in five minutes and recipes become comparable, scalable, and fixable.
The convention
Hydration = water ÷ total flour × 100. Salt % = salt ÷ total flour × 100. Starter % = starter ÷ total flour × 100.
Total flour includes the flour inside the starter (half its weight, at 100% hydration). The hydration calculator applies all of it — which is why its numbers differ from naive recipes by 5–8 points.
A worked formula
| Ingredient | Weight (500 g flour base) | Baker's % |
|---|---|---|
| Bread flour | 500 g | 100% |
| Water | 350 g | 70% |
| Salt | 10 g | 2% |
| Starter (100% hyd) | 100 g | 20% |
| True hydration | ~79% (350+50) ÷ (500+50) |
What percentages unlock
- Scaling: double the flour, every ingredient doubles — no re-derivation, no arithmetic drift.
- Comparison: two recipes side by side in percentages reveal their philosophies instantly (70% vs 82% hydration is a different hobby).
- Diagnosis: flat loaf? Check the formula before the technique — starter at 8% and salt at 1% tells a story.
- Consistency: your best-ever loaf becomes a formula, not a memory.
The bands worth memorizing
- Hydration: 65–70 easy, 70–78 artisan standard, 80+ advanced.
- Salt: 1.8–2.2% — below 1.5 tastes flat, above 2.5 tastes wrong and slows yeast.
- Starter: 15–25% typical; 10% for long overnight bulk, 30% for fast warm-kitchen bakes.
Write your next loaf in percentages, feed it to the calculators here, and the recipe stops being a stranger's essay and becomes your formula.