Enter your flour and the hydration you're after, and I'll give you the water, starter, and salt in grams — with the starter's own flour and water counted properly, so your hydration is the real number, not a guess.
| Water to add | — |
|---|---|
| Starter | — |
| Salt | — |
| Total dough weight | — |
| True overall hydration | — |
Hydration is water ÷ total flour. Because your starter is part flour and part water, I fold those amounts into the totals so the percentage you set is the percentage you actually get.
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When I first started baking sourdough, the word "hydration" sounded intimidating, like something only serious bakers with fancy ovens needed to worry about. It turns out it's one of the simplest ideas in bread, and once it clicked, my loaves got a whole lot more predictable. That's why I built this sourdough hydration calculator, so you can stop guessing and start understanding what's happening in your dough.
Hydration is just the ratio of water to flour in your dough, written as a percentage. The formula is honestly that plain: hydration = weight of water ÷ weight of flour. If you use 1000 grams of flour and 700 grams of water, that's 700 ÷ 1000 = 0.70, or 70% hydration. The flour is always the baseline, the 100%, and everything else gets measured against it.
This is where baker's percentages come in, and they're the reason bakers can share recipes that work at any size. In baker's math, the total flour is always set to 100%, and every other ingredient is expressed as a percentage of that flour weight. So a recipe might read: 100% flour, 70% water, 2% salt, 20% starter. Notice those add up to more than 100, and that's completely normal, because flour is the reference point, not the total.
The beauty of this system is that it scales effortlessly. Whether you're baking one loaf or ten, the percentages stay the same. You just decide how much flour you want and multiply everything from there. This is the same idea behind why weighing in grams beats measuring in cups for bread. Precision lets the percentages mean something.
This is the part that trips up almost everyone, and it's the thing my calculator handles for you. Your starter isn't just a leavening agent, it's made of flour and water itself, so it contributes to your total hydration. A typical starter kept at 100% hydration is equal parts flour and water by weight. So if you add 200 grams of that starter, you're really adding 100 grams of flour and 100 grams of water to your dough.
If you ignore that and only count the flour and water you add separately, your real hydration will be off. To get the true number, you add the flour from the starter to your total flour, add the water from the starter to your total water, and then divide. It's a little fiddly by hand, which is exactly why I let the calculator do it. You tell it your flour, water, and starter amounts, and it gives you your actual dough hydration.
Different breads live at different hydration levels, and knowing the range helps you aim before you ever touch the dough:
When I'm baking for my family, I usually sit somewhere in the 70–75% range. It's high enough for a lovely open crumb but not so wet that the dough fights me on the counter.
Here's the payoff for understanding all this. Higher hydration generally gives you a more open, airy crumb with those big irregular holes people chase in artisan bread. The extra water lets the dough stretch and trap more gas during fermentation. Lower hydration gives you a tighter, more uniform crumb, sturdier and easier to slice thin, which is great for sandwiches.
But wetter dough is also harder to work with. It's stickier, holds its shape less willingly, and demands better technique with stretches and folds. My honest advice: start lower, around 68–70%, get comfortable, then nudge the hydration up a few percent at a time as your hands learn the dough. There's no prize for jumping straight to 85% and ending up with a puddle.
Plug in your flour, water, and starter, and the calculator tells you your true hydration, counting the flour and water hiding inside your starter. Want a specific hydration? Set your flour and target percentage and it'll tell you how much water to add. It takes the guesswork out so you can focus on the feel of the dough.
If you want to see how my own sourdough turns out, it's over in my recipes along with the rest of what I cook. And once your dough is dialed in, you might like my matching other free tools for feeding your starter and scaling recipes. All free, all yours.
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