Reading the numbers
- Recipe hydration leaves the starter out. This is the number most recipes print.
- Hydration counts the water and the flour inside the starter. It is the true wetness of the dough.
- A starter at 100% hydration is half flour and half water by weight.
How it is calculated
- Baker's percent = ingredient weight ÷ total flour weight × 100.
- Starter flour = starter ÷ (1 + hydration ÷ 100). Starter water = starter − starter flour.
- Total flour = flour + starter flour. Total water = water + starter water.
- Hydration = total water ÷ total flour × 100.
- Feeding 1:a:b: seed = target ÷ (1 + a + b); flour = a × seed; water = b × seed.
Worked example
450 g flour, 330 g water, 10 g salt, 100 g of 100% starter: total flour 500 g, total water 380 g. Hydration 76%, salt 2%, starter 20%.