Sourdough Hydration Explained: What the Numbers Actually Mean

If you've spent any time reading about sourdough online, you've seen people throwing around numbers like "75% hydration" and "80% hydration" as though they're the secret code to great bread. And when I first started baking outside the restaurant, those numbers confused me too. But here's the thing — hydration is one of the simplest and most powerful concepts in bread baking, and once you understand it, you'll make better decisions about every loaf you bake.

The Simple Definition

Hydration is the ratio of water to flour in your dough, expressed as a percentage. That's it. If you use 500 g of flour and 350 g of water, your hydration is 350 ÷ 500 = 0.70, or 70%.

What About the Starter?

Here's where beginners often get tripped up. Your sourdough starter contains both flour and water. If you maintain a 1:1:1 starter (equal parts starter, flour, water by weight), then your starter is 100% hydration — meaning it's half flour and half water.

So when you add 100 g of 100% hydration starter to a recipe, you're actually adding 50 g of flour and 50 g of water. For casual home baking, most people don't worry about this — but if you're trying to hit a precise hydration target, you'll want to factor in your starter's contribution.

How Hydration Affects Your Bread

Hydration is not just a number on a page — it fundamentally changes the character of your bread. Here's what happens as you move up and down the hydration scale:

Low Hydration: 60–65%

At this range, your dough is stiff and easy to handle. It holds its shape well, which makes it great for shaping practice. The resulting bread tends to have a tighter, more uniform crumb (the interior structure), a chewier texture, and a thicker crust. Think bagels (around 58–62%) or many traditional European country breads. If you're just starting out, there's no shame in beginning here.

Medium Hydration: 65–72%

This is the sweet spot for most home bakers. The dough is manageable but not too stiff, and the bread has a nice balance of open crumb structure and reliable handling. The recipe in my first loaf guide sits at about 72% true hydration — right at the upper edge of this range, which gives you a good crumb without making the dough too challenging.

High Hydration: 73–80%

Now we're in territory that produces those Instagram-worthy loaves with big, irregular holes and a delicate, almost custard-like crumb. But there's a trade-off: high-hydration dough is sticky, extensible, and much harder to shape. It requires strong gluten development, confident handling, and good fermentation management. If you're getting flat loaves, dropping the hydration a few percent is often the fastest fix.

Very High Hydration: 80%+

This is advanced territory. Doughs at this hydration are extremely slack and sticky. They're used for specific breads like ciabatta, certain focaccias (check out my focaccia recipe), and some artisan pan breads where the dough is supported by a pan rather than free-standing. Don't start here unless you enjoy frustration.

Hydration Comparison at a Glance

What Changes Hydration Needs?

The "right" hydration depends on more than just your preference. Several factors come into play:

Flour type: Different flours absorb water differently. Bread flour (high protein, 12–13%) absorbs more water than all-purpose flour (10–11%). Whole wheat flour absorbs significantly more than white flour because the bran particles soak up water. If you switch from bread flour to all-purpose and keep the same hydration, your dough will feel wetter and slacker.

Protein content: Higher protein flour creates a stronger gluten network that can hold more water. This is why high-hydration bakers often reach for strong bread flour or even high-extraction flour with 13%+ protein.

Environment: In humid climates, flour absorbs moisture from the air and may need slightly less added water. In dry climates, the opposite. Altitude also affects hydration needs — higher altitudes generally require more water.

Practical Tips for Managing Hydration

Use a scale, not cups. Volume measurements for flour are wildly inconsistent — one cup of flour can weigh anywhere from 120 g to 160 g depending on how you scoop it. Weight is the only reliable way to control hydration. A basic kitchen scale that reads in 1 g increments costs less than a bag of premium flour and will transform your baking.

Wet your hands, not the dough. When handling high-hydration dough, keep a bowl of water nearby and wet your hands before touching the dough. This prevents sticking without adding extra flour, which would change your hydration and create dense pockets in the finished bread.

The Bottom Line

Hydration is a tool, not a trophy. Higher hydration does not automatically mean better bread — it means different bread. The best hydration for you is the one that matches your skill level, your flour, your schedule, and the kind of bread you want to eat. Start at 68–72%, get comfortable, and then experiment. That's how every great baker I know learned — including me.