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The hidden water in your starter
Ask two bakers for the hydration of the same sourdough and you may get two different answers. One divides the water by the flour in the bowl. The other remembers that the starter is half flour and half water and folds those in too. The second figure, often called true hydration, is the one that describes how the dough will actually feel, and it is what this calculator reports.
Use it when you are checking a recipe before you bake, comparing two recipes that list their starter differently, or deciding how much water to hold back. It suits anyone who has wondered why a “70%” dough turned out wetter than expected.
Why the number matters
Water does real work in dough. It lets gluten proteins bond into a stretchy network, it dissolves the sugars the yeast feeds on, and it turns to steam in the oven to lift the loaf. More water generally means a more open, glossy crumb but a slacker dough that is harder to shape. Less water gives a tighter crumb and a dough that holds its shape easily. A few percent either way changes how the dough behaves on the bench, so knowing the real figure helps you compare recipes fairly.
Flour matters too. Whole grain flours absorb more water than white flour, so a 75% whole wheat dough can feel firmer than a 70% white one.
Using the calculator
- Under Your dough, enter the weights of Flour, Water, Starter or levain and Salt.
- Set Starter hydration. A starter fed with the same weight of flour as water is at 100%.
- Optionally enter Target hydration (optional) to see how much water would get you there. Leave it empty to skip that part.
The main results are True hydration and Dough weight. Below them you will find the total flour and total water including the starter, Hydration ignoring the starter for comparison, and the starter and salt as a share of total flour.
Worked example
A recipe lists 800 g flour, 560 g water, 160 g starter at 100% and 16 g salt. On paper that looks like 70%. The calculator shows:
- True hydration: 72.7%
- Dough weight: 1,536 g
- Total flour, with starter: 880 g
- Total water, with starter: 640 g
- Hydration ignoring the starter: 70%
- Starter, % of total flour: 18.2%
- Salt, % of total flour: 1.82%
The starter adds 80 g of flour and 80 g of water, so the real ratio is 640 ÷ 880, not 560 ÷ 800. With a target of 78%, the calculator returns Water for 78% hydration: 606 g, and Change from your recipe: +46 g.
If your starter is a stiff 50% culture instead, change Starter hydration to 50. The same recipe drops to 67.6% true hydration, and reaching 78% now takes 654 g of water, 94 g more than listed. That gap explains why a recipe written for a liquid starter can feel tight when made with a firm one.
Practical advice
- Hold some water back. Add most of it at mixing and the rest once you feel the dough; flours from different mills absorb differently.
- Salt belongs in the conversation. It is not counted as water, but at around 2% of total flour it tightens gluten, so a salted dough feels firmer than the same dough without salt.
- Don’t chase a number for its own sake. A higher figure is not automatically better; pick the hydration you can handle comfortably and raise it slowly.
- Count every liquid. Milk, yoghurt or honey all carry water. If you use them, the true hydration is higher than this calculator shows.
- Check your starter. A starter fed at 1:1:1 but left to evaporate for days may not be 100% any more.
When you want to design a dough from scratch at a chosen hydration, the sourdough recipe builder works backwards from loaf size. For a full breakdown of every ingredient as a percentage, try the baker’s percentage calculator.
Hydration FAQ
What is a good hydration for a first sourdough loaf?
Around 68 to 72% with strong white bread flour is forgiving. It is wet enough for a decent open crumb yet firm enough to shape without it spreading into a pancake.
Should the starter really count toward hydration?
For comparing recipes, yes. A dough with 20% starter at 100% hydration carries a meaningful amount of extra water, and ignoring it makes one recipe look drier than it really is.
Why does my high hydration dough spread instead of rising?
Often the flour cannot absorb that much water, the gluten is underdeveloped, or bulk fermentation ran too long. Try a lower hydration, add more sets of folds, or shorten the rise.
Does whole wheat need more water?
Usually. Bran and germ soak up water, so whole wheat and rye doughs often need 5 to 10% more to feel as soft as a white dough. Some bakers let whole grain doughs rest after mixing so the bran can hydrate.
Is salt part of the hydration figure?
No. Hydration compares water to flour only. The calculator shows salt separately as a percentage of total flour so you can check it sits in the usual 1.8 to 2.2% range.