Hydration is against the flour, and everyone reads it wrong once
A 75% hydration dough is not 75% water. It is 75 g of water for every 100 g of flour, which makes it about 43% water by mass before the salt goes in and 42% after. The percentage is stated against flour because flour is the thing that varies between recipes, and it is the reason a formula can sum to 178% without anything being wrong.
This matters the moment you start correcting a dough. Adding 50 g of water to a 500 g flour dough moves hydration by ten points, because the denominator did not change. Adding 50 g of flour to that same dough at 80% hydration moves it 7.3 points the other way, because the denominator did change. Same 50 g, different sized effect, and only one of the two also dilutes the salt.
Two ways to fix a wet dough, and only one is cheap
| Add water | Add flour | |
|---|---|---|
| Moves hydration | Up | Down |
| Effect on salt percentage | None | Diluted |
| Effect on yeast percentage | None | Diluted |
| Effect on prefermented flour | None | Diluted |
| Needs re-mixing | A little | Properly, and dry flour in a mixed dough streaks |
Run the standard case. You have 500 g of flour and 400 g of water, which is 80%, and you wanted 70%. Adding flour, you need 400 ÷ 0.70 − 500, so 71.4 g. The dough is now 571 g of flour, and the 10 g of salt that was a clean 2.00% is 1.75%. To get back to 2.00% you add 1.4 g of salt. None of that is a disaster, but it is three changes to a formula that was one mistake, and it is why bakers hold back the last five percent of the water and decide after the flour has taken it up.
Different flours are different problems
The reason a formula lands wrong is usually not the arithmetic. Bread flour at 12 to 13% protein takes up meaningfully more water than an all-purpose at 10 to 11%, and whole grain flours keep absorbing for the first half hour because the bran hydrates slowly. A 75% formula written for one can behave like an 82% formula in the other, and the dough is not wrong, the number is just not transferable.
Whole grain has a second habit worth knowing: a dough that felt right at the mix can stiffen noticeably over the next thirty minutes as the bran takes up water. Correcting during that window means correcting toward a moving target. Letting it rest first and then judging is more reliable than any calculation.
When the fix is not worth making
If the dough is two or three points off, leave it. That is inside the variation between two bags of the same flour, and inside the error of a domestic scale weighing 400 g of water. Ten points off is worth fixing. Twenty points off usually means a units mistake somewhere — a cup read as 240 g when the flour weighed 120, or a levain counted twice — and it is faster to find that than to correct around it.
For the formula itself, the bakers percentage calculator converts between percentages and weights in both directions. If the extra water arrived inside a starter, the sourdough starter and levain build calculator splits a levain into its flour and its water so you can deduct it properly. For weighing at all, rather than measuring by cup, the cooking unit converter gives a density per ingredient instead of one number for everything.
Questions people ask
My dough is too wet. How much flour do I add?
Divide the water you have by the target hydration as a decimal, then subtract the flour you already have. With 400 g of water and 500 g of flour, aiming at 70%: 400 ÷ 0.70 is 571.4 g, minus 500, so 71.4 g of flour. Two cautions. Dry flour added to a mixed dough does not disperse on its own and leaves streaks unless you mix it in properly, and the extra flour dilutes the salt and yeast percentages, which the calculator above works out for you.
Is 75% hydration the same as 75% water?
No, and the gap is large. Hydration is water divided by flour. A dough at 75% hydration made from 500 g of flour, 375 g of water and 10 g of salt weighs 885 g, of which the water is 375 g, so it is about 42% water by mass. The convention exists because flour is the reference every other ingredient in a bread formula is measured against, and it is the single most common misreading in baking arithmetic.
Do milk and eggs count toward hydration?
It depends on whose formula you are reading, which is the honest answer. Milk is roughly 87 to 88% water by weight and whole egg about 75%, so some authors count the water fraction toward hydration and others count nothing but water. Both conventions are in print. For an enriched dough, follow the recipe weights as written and do not try to reverse-engineer a hydration number out of them, because you will not recover which convention the author used.
Why did my salt percentage change when I added flour?
Because salt is stated as a percentage of flour, and you just increased the flour. Ten grams of salt in 500 g of flour is 2.00%; the same 10 g in 571 g is 1.75%. Whether that matters depends on how far you moved: a tenth of a point is nothing, half a point is tasteable and does change how fast the dough ferments. You can add salt to a mixed dough, but it dissolves better in a little of the reserved water than sprinkled on dry.
Can I fix hydration after bulk fermentation has started?
You can add water later than most people think, but it gets harder as the gluten sets up, and working extra flour into a fermented dough tears the structure you spent the time building. If you catch it in the first few minutes it is a normal correction. If you catch it an hour in, the usual advice is to bake what you have, write down what actually went in the bowl, and correct the formula for next time rather than the dough for this one.