The number most calculators get right and most bakers get wrong
Hydration is water divided by flour. The trap is that your starter is both.
A starter at 100% hydration is half flour and half water by weight. Put 100 g of it in the bowl and you have quietly added 50 g of flour and 50 g of water that the recipe never listed.
With 500 g flour and 350 g water the arithmetic looks like 70%. Count the starter and it is 72.7%. That gap is the difference between a dough you can shape and one that spreads.
Two bakers, one disagreement worth knowing about
In January 2026 a reader named Cate worked through a 70% formula on The Perfect Loaf and showed the true figure was 73.3% once the levain was counted. The site author, Maurizio Leo, agreed and went further. He said he counts the flour and water in the levain build but omits the small seed of ripe starter used to inoculate it, which in her example would move the number again, from 73.3% to about 73.9%.
So there is no single correct stopping point, only a choice about where to stop counting. This calculator counts the starter you put in the bowl and shows you both figures, so the choice is yours rather than hidden.
The formula, including a starter that is not 100%
Most starters are kept at 100%, equal flour and water. Plenty are not. A stiff starter might be 50%, a liquid levain 125%. The split is not half and half then, and the general form is worth writing down.
| Quantity | Formula | At 100 g and 100% |
|---|---|---|
| Flour from starter | S / (1 + h/100) | 50 g |
| Water from starter | S x (h/100) / (1 + h/100) | 50 g |
| True hydration | (W + water from starter) / (F + flour from starter) | 72.7% |
S is the starter weight, h its hydration as a percentage, F the flour in the bowl and W the water in the bowl. At h of 100 the first two collapse to S over 2, which is the familiar half and half rule.
What your number means for the loaf
Hydration is not a score. It is a handling decision, and each band suits different bread.
| Hydration | What the dough is like | Suits |
|---|---|---|
| 60 to 65 | Stiff, easy to handle, potentially thicker crust | Bagels, pretzels, pizza, some pan loaves |
| 65 to 70 | Balanced, manageable, good structure | Classic breads, beginner friendly sourdough |
| 70 to 75 | Moderately open crumb, thin crust | Classic country loaves, baguettes |
| 75 to 80 | Longer mixing, tender crumb, needs skill to handle | Ciabatta, focaccia, open crumb and sandwich loaves |
| 80 plus | Longer mixing, more open crumb, custard like | High hydration loaves |
These bands are from The Perfect Loaf. One row surprises people. That source puts sandwich loaves in the 75 to 80 band rather than the low one, so it is quoted as published rather than adjusted to match expectations.
Salt, and why 2% is a convention not a law
Salt is measured against total flour, the same denominator as hydration. The Perfect Loaf gives the working range as 1.8% to 2.3% and uses 1.90% in its own formula.
Two of the three calculators ranking for this search hardcode 2% with no way to change it. The field above is editable because the range is real, and because bread with a long cold proof often wants the top of it.
Feeding ratios, and what the numbers mean
A feeding ratio is written as three numbers, seed to flour to water, by weight rather than volume. A lower ratio ripens faster because there is less food per unit of starter.
| Ratio | Worked weights | Behaviour |
|---|---|---|
| 1:1:1 | 50 g starter, 50 g flour, 50 g water | Ripens in about 4 to 5 hours |
| 1:2:2 | 10 g starter, 20 g flour, 20 g water | Low ratio, faster |
| 1:4:4 | 30 g starter, 120 g flour, 120 g water | High ratio, slower |
| 1:8:8 | 5 g starter, 40 g flour, 40 g water | May need 10 hours to ripen |
Ripening times are from Brod and Taylor and assume ordinary room temperature. Colder kitchens stretch them.
How much starter to use is less settled. Published practice ranges from about 10% of the flour weight up to 50%, with warmer kitchens using less and colder ones more. There is no single right answer, which is why the calculator takes the weight from you rather than assuming one.
Questions bakers actually ask
- Should I count the starter in my hydration?
- If you want the number to describe the dough, yes. If you are following one writer's formula, use whatever convention that writer used, because their percentages were built on it. The calculator shows both so you can match either.
- My starter is 125%, not 100%. Does that break the maths?
- No, and the formula above handles it. A 125% starter is more water than flour, so 100 g of it contributes about 44 g flour and 56 g water. Several popular calculators refuse hydrations above 100% outright.
- Why does my 70% dough feel wetter than someone else's 70%?
- Two likely reasons. They may not be counting their starter, so their real figure is higher than yours. Or your flour is thirstier. Whole grain and high protein flours absorb more water at the same stated hydration.
- Does more starter mean more hydration?
- Only if the starter is wetter than the dough. At 100% starter in a 70% dough, yes, every gram of starter nudges the true figure up. The tool shows the size of that nudge as you change the weight.
- What hydration should a beginner start at?
- The 65 to 70 band is described as balanced, manageable and beginner friendly. Dough at 80% and above is genuinely hard to shape and is the usual reason a first loaf spreads flat.
Where these numbers come from
The formulas are arithmetic and carry no measurement error. The bands, the salt range and the feeding ratios are quoted from named sources rather than averaged into a house opinion, and each is linked below.
One absence is deliberate. King Arthur Baking is a standard reference here, but its pages refuse automated fetches, so nothing on this page is attributed to it. A citation that cannot be checked is worse than no citation.