What this Sourdough Hydration Calculator does
The Sourdough Hydration Calculator estimates a dough’s total hydration as a baker’s percentage. It counts the water and flour in the main recipe and also accounts for the flour and water carried by the starter. The result is the weight of water divided by the weight of flour, expressed as a percentage.
The calculator is designed for recipes where ingredients are recorded by weight in grams. Enter the additional flour and water added to the dough, the amount of starter, and the starter’s hydration. Its description is: “Calculate total dough hydration as a baker’s percentage using the flour and water in your recipe, including the flour and water contributed by your sourdough starter.” The output label is Total Hydration.
This matters because starter is part of the dough formula. A recipe listing 500 g flour and 350 g water might appear to be 70% hydration. If it also includes 100 g of 100% hydration starter, the starter contributes 50 g flour and 50 g water. The complete formula therefore contains 400 g water and 550 g flour, for about 72.73% total hydration.
How to use the Sourdough Hydration Calculator
Weigh ingredients in grams, then enter only the flour and water added outside the starter into the recipe fields. The starter field should contain its total weight. The starter hydration field describes the ratio of water to flour in that starter, expressed as a percentage.
- Additional flour in recipe (g): Flour added separately to the mixing bowl.
- Additional water in recipe (g): Water added separately to the mixing bowl.
- Starter used (g): The starter’s full weight, including its flour and water.
- Starter hydration (%): For a starter with equal flour and water by weight, enter 100.
The default example uses 500 g additional flour, 350 g additional water, 100 g starter, and 100% starter hydration. It returns 72.73%. You can enter zero starter when a formula contains no starter, and the starter hydration then has no effect on the result. The additional flour field must be at least 1 g, keeping the calculation’s flour denominator above zero across the allowed input ranges.
Use the same units for all ingredient weights. If your scale or recipe uses ounces, convert the ingredient weights to grams before entering them. A consistent unit system is essential because the formula compares weights directly.
How the Sourdough Hydration Calculator formula works
The formula first splits the starter into its flour and water portions. For a starter weight S and hydration H, starter flour is S × 100 ÷ (100 + H). Starter water is S × H ÷ (100 + H). It adds each portion to the corresponding recipe amount, then divides total water by total flour and multiplies by 100.
In the calculator’s exact expression, ((recipe_water + starter_weight * starter_hydration / (100 + starter_hydration)) / (recipe_flour + starter_weight * 100 / (100 + starter_hydration))) * 100, the numerator is all water and the denominator is all flour. The result label is Total Hydration, shown as a percentage with two decimal places.
For the default worked example, the starter weighs 100 g at 100% hydration. It contributes 100 × 100 ÷ 200 = 50 g flour and 100 × 100 ÷ 200 = 50 g water. Total flour is 500 + 50 = 550 g. Total water is 350 + 50 = 400 g. Then 400 ÷ 550 × 100 = 72.73% total hydration.
This is a baker’s percentage, not the percentage of water in the combined dough weight. Flour is the reference ingredient and is treated as 100%. Salt and other ingredients are outside this hydration calculation.
Use cases for the Sourdough Hydration Calculator
Bakers can use the result to compare formulas, adjust starter quantities, or record a recipe in a consistent format. A calculated value is useful when a formula’s ingredients are spread across a preferment and a final mix, because it brings the flour and water contributions together.
- Compare recipes: Calculate both formulas using total flour and water, including starter, before comparing their hydration percentages.
- Document a bake: Record the result alongside ingredient weights and notes about fermentation, shaping, and the finished crumb.
- Account for a different starter: Enter the starter’s actual hydration when it is maintained at a ratio other than equal weights of flour and water.
- Check a planned change: Adjust recipe water or starter weight and observe how the calculated percentage changes.
For example, replacing a 100% hydration starter with a firmer starter changes how much flour and water each gram of starter contributes. The calculator incorporates that difference from the starter’s weight and hydration. It can help keep a written formula internally consistent when a baker changes starter maintenance or adapts a recipe.
Other factors to consider when calculating dough hydration
Hydration is a useful formula measure, but it does not fully describe how dough will feel or behave. Different flours absorb water differently. Whole grain flour, freshly milled flour, and some specialty grains can handle water differently from a refined bread flour. Protein content, flour age, and milling also affect absorption.
Room temperature, fermentation time, mixing method, and the condition of the starter influence dough handling and fermentation. Salt and inclusions such as seeds or cooked grains can change texture, while their weights are not included in this calculator’s water-to-flour ratio. Recipes that use soaked ingredients may also need a baker to decide how to record that water for consistent comparisons.
Treat the displayed percentage as a calculation from the weights and starter hydration you entered. It does not predict a guaranteed dough texture, rise, or finished loaf. Make small recipe changes, keep notes, and evaluate the actual dough during mixing and fermentation. That gives the hydration number practical context for the flour and process you use.
Frequently asked questions
What does 100% starter hydration mean?
It means the starter contains equal weights of flour and water. For example, 100 g of starter at 100% hydration contributes 50 g flour and 50 g water under the calculator’s flour-and-water model.
Is the result the percentage of water in the whole dough?
No. Total hydration is a baker’s percentage: total water divided by total flour, multiplied by 100. Other ingredients such as salt are not part of that denominator.
Should I include flour and water from the starter in the recipe fields?
No. Enter only additional flour and water in those fields. Enter the full starter weight separately, and the formula accounts for its flour and water contributions.
Can I use the calculator without starter?
Yes. Enter 0 g for starter used. The result then compares the additional recipe water with the additional recipe flour.
Why might dough feel different at the same hydration?
Flour type and absorption, fermentation, mixing, temperature, and inclusions can all affect handling. The percentage describes ingredient weights, while the dough’s behavior depends on the complete recipe and process.