A baker can write “70% hydration” on a recipe and still end up with a dough that behaves differently from another baker’s 70% dough. One reason is simple: the flour and water inside the sourdough starter may have been left out of the calculation.
When I planned bread production for Healthy Nasti Kitchen, small errors multiplied across batches. You do not need complicated software to avoid this one. You need to count all the flour and all the water.
What does 100% hydration starter mean?
A starter at 100% hydration contains equal weights of flour and water. For example, 200 g of that starter contains approximately 100 g flour and 100 g water. The starter weighs 200 g, but it is not 200 g of additional water.
A stiff starter is different. A 50% hydration starter contains 50 g water for every 100 g flour. The hydration of your starter therefore matters when you calculate the finished dough.
A worked example: the real hydration of a loaf
Suppose your mix uses the following ingredients. These numbers are an illustrative calculation, not a claim about a tested Healthy Nasti Kitchen recipe.
- 500 g flour added directly to the bowl
- 325 g water added directly to the bowl
- 100 g ripe starter at 100% hydration
- 10 g salt
That 100 g of starter contributes 50 g flour and 50 g water. The total flour is therefore 500 + 50 = 550 g. The total water is 325 + 50 = 375 g.
True dough hydration = total water ÷ total flour × 100. In this example: 375 ÷ 550 × 100 = 68.2% (rounded).
If you divided only the water added to the bowl by the flour added to the bowl, you would get 325 ÷ 500 = 65%. That figure describes the separately added ingredients, not the complete dough.
What changes with a stiff starter?
Now imagine using 150 g of starter at 50% hydration. That starter contains 100 g flour and 50 g water. If you add it to the same 500 g flour and 325 g water, your totals become 600 g flour and 375 g water.
The finished dough is 62.5% hydration. The starter is heavier, yet the finished dough is less hydrated than in the first example. That is why a starter’s weight alone cannot tell you how much water it contributes.
Three calculations worth keeping on your batch sheet
- Total flour: flour added to the mix plus flour inside the starter.
- Total water: water added to the mix plus water inside the starter.
- True hydration: total water divided by total flour, expressed as a percentage.
For a starter with hydration expressed as a decimal, its flour contribution is starter weight ÷ (1 + starter hydration). Its water contribution is the starter weight minus that flour contribution. For 100% hydration, use 1.00; for 50%, use 0.50.
Keep salt and any other ingredients visible in the formula too, but do not add them to the flour-and-water hydration calculation. Ingredients such as milk, eggs, oil or inclusions need separate consideration; this simple calculation assumes flour, water, starter and salt.
Why this matters when you scale production
A single loaf can tolerate a scribbled formula. A microbakery running several dough tubs cannot afford ambiguous records. If the baker on the next shift interprets “70% hydration” differently, the dough can be inconsistent even when everybody thinks they followed the same recipe.
Write down the starter hydration, starter weight, total flour, total water and target dough weight. When you increase a batch, scale the ingredient weights consistently rather than guessing extra water by feel.
And remember: hydration is only one part of dough behaviour. Flour absorption, temperature, fermentation and handling all influence how the dough feels. I explain the flour side in Stop Chasing 80% Hydration.
A simple next step
Take one of your current formulas and recalculate it with the flour and water in your starter included. If the result differs from the percentage written in your recipe book, update the record before your next production day.
For more help with quantities, explore the Sourdough Precision recipe calculator. And if you are building a microbakery, the one-page batch sheet is a practical place to record your production figures.
By Giuseppe Nasti — Healthy Nasti Kitchen and SA Bakery Supplies. The worked numbers above are mathematical examples, not results of a baking trial.
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