What is dough hydration? The number that predicts your bread

Hydration is water as a percentage of flour

Dough hydration is the weight of the water divided by the weight of the flour, times 100. A dough with 350g of water and 500g of flour is at 70% hydration. That's the whole definition.

Notice what it is not: it's not the percentage of the dough that is water. A 70% hydration dough is not 70% water; it's roughly 40% water by total weight. Hydration is a ratio against flour, and that distinction comes from a system called baker's percentage, where flour is always the reference at 100% and every other ingredient is measured against it. If that system is new to you, the baker's math guide covers it from the ground up.

Why anchor everything to flour? Because it makes recipes portable. A 70% hydration dough behaves the same whether you make one loaf or twenty. Doubling a recipe changes every gram figure and changes the hydration not at all. Professional bakers describe doughs to each other this way for exactly this reason: the percentage is the recipe.

How to calculate it, in both directions

From amounts to a percentage: divide water by flour, multiply by 100.

So 340g of water on 500g of flour is 340 ÷ 500 × 100 = 68%. From a target percentage to a water weight, run it backwards.

Want 75% hydration on 500g of flour? That's 500 × 0.75 = 375g of water. Both directions are trivial until a sourdough starter enters the bowl, which is where the arithmetic gets interesting and where the dough hydration calculator earns its keep.

One convention worth knowing: “water” here means all the liquid that hydrates the flour. Milk, beer, and juice count (milk is about 87% water, so precise bakers discount it). Butter and eggs contribute moisture too, which is why enriched doughs feel wetter than their stated hydration.

What each hydration level feels like

The number maps directly onto how the dough behaves under your hands, which is why bakers care about it more than any other percentage.

55–60%: stiff. Bagel and pretzel territory. The dough is dense, dry to the touch, and takes real effort to knead. It holds any shape you give it, which is exactly what you want when the dough has to survive a trip through boiling water.

60–65%: standard. Sandwich loaves and pan breads. Smooth, soft, obedient. It shapes cleanly, rises evenly, and gives the tight, even crumb you want for toast and slicing.

65–70%: moderate. The country loaf window and the best place to learn sourdough. Slightly tacky but still workable, with a semi-open crumb. Most beginner-friendly artisan recipes live here on purpose.

70–80%: high. Classic artisan sourdough. The dough is slack and sticky, spreads on the bench if unsupported, and needs stretch-and-folds rather than kneading. The reward is the open, irregular, glossy crumb bakeries photograph.

80% and up: very high. Ciabatta and focaccia. At this level you stop shaping in any traditional sense; wet hands, oiled pans, and confidence are the technique. The crumb can be spectacular, and the dough will test your patience getting there.

Two caveats keep these ranges honest. Whole-grain flours drink 5–10% more water than white flour, so a 78% whole wheat dough handles like a low-70s white dough. And flour strength matters: a high-protein bread flour holds high hydration together; the same water in a weak flour makes soup.

The starter problem: true vs apparent hydration

Here is the part most recipes get wrong. A sourdough starter is not a single ingredient; it is flour and water that fermented together. A starter kept at 100% hydration, fed equal weights of flour and water, is half of each. Add 100g of it to your dough and you have added 50g of flour and 50g of water, whether or not the recipe admits it.

That means every sourdough recipe has two hydration numbers. The apparent hydration counts only the water and flour you added directly. The true hydration counts what the starter brought too. Take a recipe with 500g of flour, 340g of water, and 100g of 100% starter. Apparent: 340 ÷ 500 = 68%. True: total flour is 550g, total water is 390g, and 390 ÷ 550 = 70.9%. Nearly three points of drift, in a craft where bakers argue over one.

The gap grows with the amount of starter, and it inverts with a stiff starter (kept below 100% hydration, so it carries more flour than water). This is why a dough from a starter-blind recipe so often feels wetter than the number promised. The calculator reports both numbers, and its water mode subtracts the starter's water before telling you what to pour.

Choosing a hydration on purpose

Once you can calculate hydration, you can start choosing it instead of inheriting it. The decision has three inputs: the bread you want, the flour you have, and your comfort with wet dough.

Chasing an open, holey crumb? Move up the scale, a couple of points per bake, and learn the folding technique that keeps slack dough structured. Getting flat loaves that spread on the peel? Come down 3 to 5 points; strength problems masquerade as flavour problems less often than the reverse. Switching to whole wheat or rye? Add water to keep the same feel, because the stated percentage no longer means what it did with white flour.

And when a dough finally feels right in your hands, calculate its true hydration and write it down. That single number, more than any recipe card, is the thing you'll reach for next time.

References

1. King Arthur Baking Company. Hydration in bread dough, explained. kingarthurbaking.com
2. The Perfect Loaf. What Is Dough Hydration? (And How to Get It Right). theperfectloaf.com
3. Hamelman, J. Bread: A Baker's Book of Techniques and Recipes. 2nd ed. John Wiley & Sons, 2012. The professional reference for hydration across lean and sourdough breads.
4. Reinhart, P. The Bread Baker's Apprentice. Ten Speed Press, 2001. Classifies doughs from stiff (bagels) through rustic (ciabatta) by water content.
5. Forkish, K. Flour Water Salt Yeast. Ten Speed Press, 2012. High-hydration technique for home bakers.