🍞 Baking
Baker's percentages and hydration, explained
Professional bread recipes look strange at first: the flour is 100 percent, the water is 75 percent, and the numbers add up to far more than 100. Once you see what the percentages are measuring, they become the most useful numbers in the kitchen.
Flour is the fixed point
In baker's mathematics, the total weight of flour is always 100 percent, and every other ingredient is expressed as a percentage of that weight. Water at 75 percent means 750 grams of water for every kilogram of flour. Salt at 2 percent means 20 grams. The percentages deliberately do not add up to 100, because they are ratios to flour rather than shares of the dough.
This is not a peculiar tradition; it is the only way to write a formula that behaves consistently. Doubling a recipe written in cups changes the hydration unpredictably, because the flour compacts differently at different volumes. Doubling a formula written in percentages changes nothing about the dough at all.
A formula, converted to grams
| Ingredient | % of flour | Weight |
|---|---|---|
| Bread flour | 100% | 1,000 g |
| Water | 75% | 750 g |
| Salt | 2% | 20 g |
| Instant yeast | 1% | 10 g |
| Total dough | 178% | 1,780 g |
The total percentage — 178 percent — is the yield. Divide the dough weight you want by the total percentage and multiply by 100 to get the flour weight. Want two 900 g loaves from this formula? 1,800 ÷ 178 × 100 = 1,011 g of flour, and every other ingredient follows from that.
The leaven and baking scaler does this conversion, including the awkward case where you are scaling a sourdough starter rather than a straight dough.
Hydration by bread style
Hydration is the water percentage, and it is the single number that most affects how a dough handles. These are typical ranges rather than rules; flour strength, shaping skill and proofing all shift what works.
| Style | Hydration | What to expect |
|---|---|---|
| Bagel, pretzel | 50–58% | Stiff, easy to shape, dense chew |
| Brioche, enriched | 50–60% added water | Soft and rich; much wetter once eggs, milk and butter are counted |
| Sandwich loaf | 60–65% | Firm enough for a tin, soft crumb |
| Baguette, pizza | 65–70% | Open but manageable; needs good gluten |
| Sourdough country loaf | 70–80% | Open crumb, slack dough, more folding |
| Ciabatta, focaccia | 80–90% | Very slack; handled with wet hands and folds |
Water hides in other ingredients
A brioche written at 10 percent added water is not a dry dough. Milk is roughly 87 percent water, whole egg about 76 percent, and butter about 16 percent. Take a formula with 1,000 g flour, 500 g egg, 200 g milk, 400 g butter and 100 g water: the water contributed is 380 + 174 + 64 + 100 = 718 g, so the true hydration is about 72 percent. The dough behaves like a 72 percent dough because that is what it is.
This matters when comparing recipes from different books. If one author counts only added water and another counts all water, the same loaf can appear to have two different hydrations. When a recipe's numbers look unusually low for its description, check whether the eggs and dairy have been counted.
Salt and yeast, in the same units
Salt is normally 1.8 to 2.2 percent of flour weight — 18 to 22 grams per kilogram. Below about 1.5 percent the bread tastes flat and the crust browns unevenly; above 2.5 percent it tastes salty and fermentation slows, because salt inhibits yeast.
Yeast depends entirely on time and temperature. Instant yeast at 1 percent gives a same-day rise at room temperature. At 0.5 percent it needs longer; at 0.1 to 0.2 percent in a cold retard it can ferment overnight in the fridge. Sourdough starter at 20 percent of flour weight is a typical inoculation, but the percentage alone does not determine timing — the temperature does at least as much.
Preferments: two sets of numbers, one dough
Poolish, biga and levain are all pre-fermented portions of flour, water and a leavening agent. When a formula includes one, you have to decide whether its flour and water count towards the total. Professional formulas almost always include them, and list the preferment separately as a breakdown. That way the headline hydration describes the actual dough.
| Preferment | Hydration | Typical use |
|---|---|---|
| Poolish | 100% | A pinch of yeast; 12 to 16 hours. |
| Biga | 50–60% | Stiffer; often used for Italian breads. |
| Levain | Usually 100% | Built from a maintained starter. |
If 200 g of flour in a 1,000 g formula is fermented as a 100 percent poolish, that is 200 g flour and 200 g water. The remaining 800 g of flour and 550 g of water bring the total to 750 g water per 1,000 g flour — still 75 percent, provided you account for both components.
Adjusting a dough that is not behaving
Hydration numbers are a starting point, not a guarantee. Flour absorbs differently from harvest to harvest, and a dough that is 75 percent on paper can feel like 80 percent in a humid kitchen. The professional fix is to hold back 5 percent of the water and add it only if the flour takes it.
If a dough is too slack to handle, add flour in 1 percent increments and rest before judging — gluten needs twenty minutes to hydrate and relax. If it is too stiff, add water a tablespoon at a time. Chilling the dough makes it firmer and easier to shape but slows fermentation, so do not use the fridge as a shaping aid without adjusting the timings.
Frequently asked questions
Sources
- USDA FoodData Central — water content of milk, egg and butter.
- Jeffrey Hamelman, Bread: A Baker's Book of Techniques and Recipes — professional formula conventions and preferments.
- King Arthur Baking, ingredient and hydration reference material.