How to Calculate Sourdough Hydration (the Right Way)
Hydration is the single number that most defines a bread dough: the weight of water as a percentage of the weight of flour. Bakers track it in baker's percentages, where flour is always 100% and everything else is measured against it. Get the hydration right and you can predict how the dough will feel and how open the crumb will be; get it wrong and you're guessing.
The catch with sourdough is the starter. Your levain is itself a mix of flour and water, so it quietly changes the dough's true hydration — and most calculators ignore it. A 100%-hydration starter is half flour and half water by weight, so 100 g of starter adds 50 g of flour and 50 g of water to your totals. This calculator splits the starter for you and folds it into the real flour and water figures, so the hydration you see is the hydration you'll actually feel. It even shows the naive number — what you'd get ignoring the starter — so you can see how much difference it makes.
What different hydrations feel like
| Hydration | Typical breads | How the dough handles |
|---|---|---|
| 55–65% | Bagels, pretzels, sandwich loaves | Stiff, easy to shape, tight crumb |
| 65–72% | Classic sourdough boules, batards | Workable with light stickiness — the beginner sweet spot |
| 72–80% | Rustic country loaves, pain de campagne | Slack and sticky; needs stretch-and-folds, rewards with open crumb |
| 80–90%+ | Ciabatta, focaccia, high-hydration city loaves | Pourable-soft; coil folds and confident handling required |
Whole-grain and high-protein flours absorb more water, so a 75% whole-wheat dough handles like a lower-hydration white dough — adjust by feel, a few percent at a time.
Targeting a hydration
Working the other way is just as useful. Set a target hydration and the calculator tells you how much water to use with your chosen flour and starter — accounting, again, for the water already in the levain. Pair it with a kitchen scale and you can hit the same hydration batch after batch. When your recipe is dialled in and it's time to bake, our oven temperature converter covers the Fahrenheit, Celsius, gas-mark and fan settings.