How to Calculate Sourdough Hydration (the Right Way)
Hydration is the single number that most defines a bread dough: the weight of water as a percentage of the weight of flour. Bakers track it in baker's percentages, where flour is always 100% and everything else is measured against it. Know the hydration and you can predict how the dough will feel before you mix it.
The catch with sourdough is the starter. Your levain is itself a mix of flour and water, so it changes the dough's true hydration, and a simple water ÷ flour sum leaves it out. A 100%-hydration starter is half flour and half water by weight, so 100 g of starter adds 50 g of flour and 50 g of water to your totals. This calculator splits the starter for you and folds it into the real flour and water figures. It also shows the naive number, what you'd get ignoring the starter, so you can see the difference: 70% against 73% with the default dough. With a stiff starter the naive number reads high instead of low.
What different hydrations feel like
| Hydration | Breads (King Arthur's published %) | How the dough handles |
|---|---|---|
| Under 65% Firm to stiff | Bagels, pretzels and other firm, close-crumbed doughs Easiest Loaf of Bread 63% | Firm or even stiff; easy to shape, tighter crumb |
| 65–72% Moderate | Everyday white and French loaves French bread 65% · White bread 66% | Soft and a little tacky, but holds its shape for hand-shaping |
| 72–80% Slack | Country-style sourdough, some ciabatta Ciabatta 73% · Country-style sourdough 77% | Slack and sticky; folds during the rise build strength |
| 80% and up High hydration | Pain de campagne, wetter ciabatta, pan de cristal Pain de Campagne 80% · Ciabatta (baker's-math lesson) 82% · Pan de Cristal 100% | Very slack — what King Arthur calls high hydration |
The band cut-offs are our own rough guide, not a published standard. King Arthur's hydration guide says doughs at 55–65% "will likely feel firm or even stiff" and reserves high hydration for doughs "often in excess of 80%"; our cut-offs follow that, except that we start Moderate at 65%, the top of King Arthur's firm range. The calculator's label uses the same bands.
Whole-grain flours are thirstier, so a 75% whole-wheat dough feels firmer than a 75% white dough. Adjust by feel, a few percent at a time.
Targeting a hydration
Working the other way is just as useful. Set a target hydration and the calculator tells you how much water to use with your chosen flour and starter, accounting again for the water already in the levain. Pair it with a kitchen scale and you can hit the same hydration batch after batch. Want every ingredient as a percentage, or to scale the dough to a number of loaves? Use the baker's percentage calculator. When it's time to bake, the oven temperature converter covers Fahrenheit, Celsius, gas mark and fan settings.
Sources
- King Arthur Baking, Hydration in bread dough, explained: counting the starter's flour and water, the firm and high-hydration ranges, and the Easiest Loaf, country-style sourdough, Pain de Campagne and Pan de Cristal figures.
- King Arthur Baking, Baker's percentage: the white bread, French bread and 73% ciabatta formulas.
- King Arthur Baking, What is baker's math?: the 82% ciabatta formula.