Free tool
Sourdough hydration calculator
Type in your flour, water and starter in grams. See the hydration your dough really has once the starter's own flour and water are counted, the water you need for the number you want, and the whole recipe scaled to any loaf size.
What hydration means
Hydration is the water in a dough as a percentage of the flour weight, with the flour always counted as 100 percent. That is the baker's percentage method, and it is why bakers can compare a 500 g loaf with a 2 kg batch at a glance. With 500 g flour and 375 g water, the dough is 75 percent hydration. With 500 g flour and 325 g water, it is 65 percent.
It is the one number that most changes how a dough feels in your hands, and whether the crumb comes out tight and even or loose and glossy.
Why your recipe is wetter than it looks
Most sourdough recipes list the starter as its own line, and the flour and water inside it are easy to forget. A starter fed equal weights of flour and water is a 100 percent hydration starter: half of its weight is flour and half is water. This calculator counts it that way, as nearly every home recipe does, and shows you the true hydration.
| Recipe line | Grams | Flour counted | Water counted |
|---|---|---|---|
| Bread flour | 500 | 500 | 0 |
| Water | 350 | 0 | 350 |
| Starter at 100 percent | 100 | 50 | 50 |
| Total | 950 | 550 | 400 |
The recipe looks like 70 percent (350 over 500). Counted properly it is about 73 percent (400 over 550). Three points is the difference between a dough that shapes cleanly and one that sticks. If your starter is stiffer or wetter than equal parts, enter its hydration and the calculator splits it accordingly. Salt is listed with the recipe but does not change the hydration.
What the numbers feel like
| Hydration | How the dough feels | What the crumb tends to do |
|---|---|---|
| About 65 percent | Firm, smooth, easy to shape | Tighter, even, good for sandwich loaves |
| About 70 percent | Soft but manageable | A friendly middle for first loaves |
| About 75 percent | Soft and a little tacky, needs a few sets of folds | Lighter and more varied |
| About 85 percent | Slack, sticky, almost batter at first | Can be very open and glossy, with practiced hands |
Higher is not automatically better. A well fermented 70 percent loaf beats a poorly handled 85 percent one every time, because the open crumb people chase comes mostly from good fermentation and shaping, with water as a helper. If you are on your first few loaves, start around 68 to 72 percent and raise the water by 2 to 3 points only once two loaves in a row come out the same.
Hitting a hydration you choose
Pick the hydration you want and the calculator gives you the water to add, after allowing for the water already in your starter. It is the quickest way to move a recipe up or down a few points without redoing the arithmetic by hand.
When you mix, hold back about 25 to 50 g of that water and work it in slowly. Flour varies between bags, even of the same type, and humidity in your kitchen changes how much it takes. If the dough starts to feel loose and hard to handle before the water is all in, stop: you have found your flour's limit for today. Wet hands or a bench scraper help with a sticky dough far better than extra flour, which quietly lowers the hydration as you go.
Scaling to a dough weight
Want a bigger loaf, two loaves, or a smaller one for a small pot? Enter the total dough weight you want and every line scales together, starter included, so the hydration and salt stay exactly where they were. Round the grams to whole numbers on your scale; a gram here or there makes no difference to the dough.
Try it
Once the recipe is set, the bake planner works back from the time you want bread out of the oven to when you should feed the starter, mix, fold, shape and proof.
Whole grain, rye and the water they drink
Whole wheat, rye and spelt keep their bran and germ, and bran soaks up a lot of water. A whole wheat dough at 80 percent can feel about as firm as a white dough at 70 percent. When you swap in some whole grain, add water too, often 5 to 10 percent more, and give the dough a rest so the bran can absorb it. Rye has little gluten strength and turns sticky and paste-like at almost any hydration, so it bakes into a tighter, denser crumb whatever you do. That is its nature, not a fault.
Read more in sourdough hydration explained and baker's percentage for sourdough.
Sources
Hydration as a percentage of flour weight, with flour at 100 percent, follows the standard baker's percentage method taught in baking schools; the formula and the advice to hold back some water follow The Perfect Loaf's guide to dough hydration; counting the starter as half flour and half water follows common home baking practice and the Loaf Scout app. Each linked guide names its sources in full. The calculator is arithmetic on the numbers you type and runs entirely in your browser.
Questions
Does the starter count toward hydration?
Yes, if you want the dough's true hydration. A starter fed equal weights of flour and water is half flour and half water, so 100 g of starter adds 50 g to the flour and 50 g to the water. Most home recipes count it this way.
What hydration should a beginner use?
Around 68 to 72 percent. The dough is soft enough to open up but firm enough to shape and read. Raise it by 2 to 3 points at a time once two loaves in a row come out the same.
How much water do I need for 75 percent hydration?
Multiply the total flour by 0.75, then subtract the water already in your starter. With 500 g flour and 100 g of a 100 percent starter, total flour is 550 g, so total water is about 413 g, and you add about 363 g.
Why does my high hydration dough feel wetter than the number says?
Usually the starter was not counted, the flour is weaker or finer than the recipe's, or the kitchen is humid. Hold back 25 to 50 g of water and add it only if the dough can take it.
Does salt change the hydration?
No. Salt is listed as its own baker's percentage, often around 2 percent of the flour, but hydration is only water over flour.
Is this calculator a recipe?
No. It is arithmetic on the grams you enter. Loaf Scout gives an AI read of one photo; your own eyes, nose and the poke test still count, and so do your hands on the dough.