When bakers talk about a dough being "70% hydration" or "80% hydration," they're describing the ratio of water to flour by weight — not the total moisture in the dough, and not a percentage of anything to do with volume. It's calculated with a simple formula, part of what's called baker's percentage, where every ingredient is expressed as a percentage of the total flour weight:
So if a recipe uses 500 g of flour and 375 g of water, that's 75% hydration. Flour is always the 100% baseline — everything else (water, salt, yeast, oil) is expressed relative to it. This is also why baker's percentages in a single recipe can add up to well over 100%: they're not parts of a whole, they're each ingredient's weight relative to the flour.
| Bread type | Typical hydration | Texture |
|---|---|---|
| Sandwich loaf / pan bread | 60–65% | Tight, easy to slice |
| Standard artisan loaf | 65–70% | Balanced, moderate open crumb |
| Rustic / country loaf | 70–75% | Open, chewy crumb |
| Baguette | 68–75% | Airy with a crisp crust |
| Ciabatta | 75–85% | Very open, irregular holes |
| Focaccia | 80–90% | Soft, extremely open crumb |
| Pizza dough (Neapolitan-style) | 60–65% | Pliable, stretchy |
Higher hydration generally means a more open, irregular crumb with larger air pockets, and a thinner, crisper crust — but it also means a wetter, stickier dough that's harder to shape by hand. Lower hydration gives a tighter, more even crumb and a dough that's easier to handle, at the cost of some of that airy texture.
Say you want to try a rustic loaf at 72% hydration, and your recipe calls for 500 g of flour. Rearranging the formula to solve for water weight:
500 g × 0.72 = 360 g of water. That's it — no conversion charts needed once you're thinking in weight rather than volume, which is exactly why a kitchen scale (see our kitchen scale buying guide) matters so much more for bread than for most other cooking.
| Flour | 65% hydration | 72% hydration | 80% hydration |
|---|---|---|---|
| 500 g | 325 g water | 360 g water | 400 g water |
| 750 g | 488 g water | 540 g water | 600 g water |
| 1000 g | 650 g water | 720 g water | 800 g water |
Flour doesn't have a fixed volume-to-weight relationship — how it's scooped, whether it's sifted, and even the specific flour's protein content all change how much a cup actually weighs. A "cup of flour" can reasonably vary by 15–20%, which at bread-baking hydration levels is enough to turn a workable dough into either a dry brick or a batter-like mess. Water, by contrast, has a fixed weight (1 mL ≈ 1 g), so once you're measuring both flour and water by weight, the ratio between them is exact every time. This is the same reasoning covered in our cooking conversions guide — it just matters more here, because bread dough is far less forgiving of measurement error than most other baking.
Once you're working in grams for flour and water, it's worth doing the same for salt, yeast, and any mix-ins — baker's percentage really only pays off when the whole recipe is weighed consistently. For any leftover volume measurements a recipe gives you, the Mass category and Imperial ⇄ Metric category on the UnitDial converter handle the rest.