What hydration is, and what it changes
Hydration is water weight divided by flour weight, expressed as a percentage. A dough made from 1,000 g of flour and 700 g of water is at 70% hydration. The convention comes from baker's percentage, where flour is always the 100% that everything else is measured against — the same system the baker's percentage calculator uses for the rest of the formula.
The number matters because water is what makes gluten mobile. At low hydration the gluten network is tight and the crumb comes out fine and even; at high hydration the network is loose, gas bubbles merge before the crust sets, and you get the irregular open crumb people photograph. Water also dilutes everything else: the same 2% salt is a lower concentration in the aqueous phase of a wet dough, so fermentation runs marginally faster.
What hydration does not do is guarantee a result. The same 78% on a strong Canadian bread flour and on a soft supermarket all-purpose flour produce completely different doughs, because absorption is a property of the flour: protein quantity, degree of starch damage from milling, and the presence of bran all pull water. Whole grain and freshly milled flours keep absorbing for half an hour or more after mixing, which is why a dough that felt loose at the end of mixing can feel correct after an autolyse.
Treat a published hydration as a starting point for someone else's flour and adjust yours by feel — then record the figure that worked, so it becomes repeatable.
The water you are not counting
The formula is simple; getting the numerator right is where it goes wrong. Three categories of water routinely escape the count.
Non-water liquids. Milk, eggs, cream, juice and beer are mostly water by weight. Using USDA FoodData Central composition data, whole milk is about 88% water, raw whole egg about 76%, and butter about 16%. A brioche with 200 g of milk, 150 g of egg and 250 g of butter on 500 g of flour carries 176 + 114 + 40 = 330 g of water — 66% hydration — even though the formula lists no water at all.
Flour and water inside a preferment. A levain, poolish or biga is part flour and part water, and both parts belong in the totals. Counting a 200 g levain at 100% hydration as leaven rather than as 100 g of flour plus 100 g of water understates the true hydration of the final dough. The sourdough starter hydration calculator does that split for you.
Wet inclusions. Soakers, cooked grains, boiled potato, roasted vegetables and rehydrated fruit all bring water. A tangzhong or scald is water that has already been bound by gelatinised starch — it still counts in the numerator, but it behaves quite differently in the hand.
Fat is the mirror image: oil, shortening and lard contain no water at all, so they contribute nothing to hydration while making the dough feel softer. That contradiction is why an enriched dough often feels far wetter than its calculated hydration suggests.
Worked example: an enriched dough with no water in the recipe
A soft roll formula calls for 500 g flour, 200 g water, 100 g whole milk, 50 g whole egg and 50 g butter. Work out the true hydration and what it takes to reach 75%.
- Water from milk. 100 g × 0.88 = 88 g.
- Water from egg. 50 g × 0.76 = 38 g.
- Water from butter. 50 g × 0.16 = 8 g.
- Total water. 200 + 88 + 38 + 8 = 334 g.
- Hydration. 334 ÷ 500 × 100 = 66.8%. Counting only the poured water would have given 200 ÷ 500 = 40%, which is not a dough that exists.
- Water at a 75% target. 500 × 0.75 = 375 g.
- Water to add. 375 − 334 = 41 g.
Now run the correction the other way. Suppose you overshot and mixed 800 g of water into 1,000 g of flour — 80% hydration — when you wanted 70%. You cannot remove water from a mixed dough, so the fix is flour: you need a flour weight F' such that 800 ÷ F' = 0.70, giving F' = 800 ÷ 0.70 = 1,142.86 g. That is 142.86 g of flour to add. Note that the two corrections are never both positive: if the water gap is negative, the flour figure is positive, and vice versa. They are zero together only when the dough is already exactly on target.
What hydration figure to aim for
Match the hydration to the product and to the flour, in that order. The bands below are the ones working bakers use, and they hold for a bread flour of roughly 12-13% protein.
50-58% is stiff-dough territory: bagels, pretzels, some crackers and pasta. These doughs need a serious mixer or a sheeter, and they hold their shape without any support.
60-65% covers sandwich pan loaves, brioche, enriched buns and most pizza doughs mixed the night before. The dough is smooth, easy to shape and forgiving of imprecise handling.
65-72% is the standard range for a lean hearth bread: baguettes, batards, and most yeasted country loaves. This is where a beginner should start with any new flour.
72-82% is where the open, irregular sourdough crumb lives. It requires strong flour, folds rather than kneading, and a proofing basket. Handling matters more than the number here.
Above 85% the dough will not hold a free-standing shape without either a tin or a flour strong enough to build a network under that much water. Ciabatta and some focaccia are made this way deliberately.
If your figure sits well outside the band for what you are making, check the numerator before you change the recipe — a missed levain or an uncounted soaker is the usual explanation.
Water content of common dough liquids
| Ingredient | Water by weight | Water in 100 g |
|---|---|---|
| Water | 100% | 100 g |
| Whole milk (3.25% fat) | 88% | 88 g |
| Whole egg, raw, shelled | 76% | 76 g |
| Egg white, raw | 88% | 88 g |
| Egg yolk, raw | 52% | 52 g |
| Heavy cream | 58% | 58 g |
| Plain yoghurt, whole milk | 88% | 88 g |
| Butter, salted | 16% | 16 g |
| Honey | 17% | 17 g |
| Vegetable oil, lard, shortening | 0% | 0 g |
Composition figures are rounded from USDA FoodData Central entries for each ingredient. Round numbers are close enough: a one-point error on a liquid that is 15% of the formula moves hydration by well under a percentage point.
Absorption is a flour property, not a recipe property
Millers publish a water absorption figure for commercial flours, measured on a farinograph as the water needed to bring a dough to a standard consistency of 500 Brabender units. It is the closest thing to an objective hydration target that exists, and it is printed on the spec sheet for most professional flours. If you can get that number for your flour, start there rather than at a hydration you read online.
Absorption rises with protein content, with starch damage from harder milling, and sharply with bran content — which is why a 20% whole wheat substitution usually needs 3-5 percentage points more water to feel the same in the hand.
Common hydration mistakes
- Counting only the poured water. Milk, egg and butter are mostly water. An enriched dough calculated on poured water alone can be understated by 25 percentage points or more.
- Leaving the levain out of both totals. A preferment carries flour as well as water. Add its flour to the denominator and its water to the numerator, or the figure is meaningless.
- Measuring liquids by volume. Water is close enough to 1 g per ml that it hardly matters, but milk, honey and oil are not — weigh them.
- Chasing a hydration from a photograph. The number that gave someone else an open crumb was matched to their flour, their mixer and their proofing temperature.
- Judging the dough before the autolyse finishes. Whole grain and freshly milled flours keep taking up water for 30 minutes or more after mixing.
- Adding water to a dough that is already too wet. Water cannot be removed once mixed. The correction is flour, and it changes every other percentage in the formula with it.
- Ignoring humidity in stored flour. Flour equilibrates with the air; a bag opened in a damp kitchen in August carries more water than the same bag in a dry January.
Where hydration fits with the rest of the formula
Hydration is one of four numbers that define a dough: hydration, salt, leaven and temperature. Changing any one of them changes what the others do.
Raise hydration and fermentation accelerates slightly, because the yeast has a more dilute, more mobile medium to work in and the salt concentration in the water phase drops. Raise dough temperature and it accelerates a great deal more — the desired dough temperature calculator is the tool that makes that variable controllable rather than accidental, and it uses the total water weight this page reports.
Hydration also sets the ceiling on how much flour a given volume of dough contains, which is why pizzerias specify both a hydration and a dough ball weight. If you are working towards a fixed number of pizzas rather than a fixed flour weight, start from the pizza dough ball calculator instead and let it size the flour for you.
Two things this calculator deliberately does not model: bake loss, which removes 10-15% of a hearth loaf's weight as steam after the arithmetic ends, and the effect of altitude on evaporation during proofing and baking, which the high altitude baking adjustment calculator covers. Neither changes the hydration you mix at; both change what comes out of the oven.