Sourdough hydration calculator
Enter the flour, water and starter in your recipe to get the true hydration — counting the flour and water inside the starter, which most recipes leave out.
Hydration 75%
The formula
hydration = (water + starter water) ÷ (flour + starter flour) × 100. A starter at h% hydration contains starter ÷ (1 + h/100) of flour; the rest is water. For a 100% starter that is simply half and half.
Example: 450 g flour, 325 g water and 100 g starter at 100% → (325 + 50) ÷ (450 + 50) = 375 ÷ 500 = 75%. Ignore the starter and you would call it 72.2%.
How much the starter changes hydration
| Recipe (flour + water) | Starter | Without starter | True hydration |
|---|---|---|---|
| 500 g + 350 g | 100 g at 100% | 70% | 72.7% |
| 500 g + 350 g | 100 g at 50% | 70% | 67.6% |
| 1000 g + 700 g | 200 g at 100% | 70% | 72.7% |
| 1000 g + 750 g | 200 g at 100% | 75% | 77.3% |
| 1000 g + 700 g | 300 g at 100% | 70% | 73.9% |
A stiff starter (50% hydration) adds more flour than water, so it lowers true hydration slightly; a liquid starter raises it. To build a whole recipe around a target hydration, with the levain taken out automatically, use the baker's percentage calculator. The sourdough hydration guide explains levain percentages and prefermented flour in depth.
FAQ
Do you count the starter in hydration?
Yes. True hydration is the total water, including the starter's water, divided by the total flour, including the starter's flour. A 100% hydration starter is half flour and half water.
What hydration should my sourdough be?
Most country loaves are 70–80%. Start around 70–72% while learning to shape, and add 5% or more water for whole-grain flour.
What is starter percentage (inoculation)?
The weight of starter as a percentage of total flour. 100 g starter in a dough with 500 g total flour is 20%; at 100% hydration that is 10% prefermented flour.