Baker’s Percentage: Read a Bread Formula Without Guessing
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When a baker calls a dough “70% hydration,” that doesn’t mean water makes up 70% of the dough. It means the water weighs 70% as much as the flour. Once that clicks, bread formulas become much easier to read.
Baker’s percentage uses the total flour weight as its reference. Flour is always 100%, and every other ingredient is compared with it. That’s the system set out in King Arthur’s professional baking reference. The percentages can add up to more than 100 because they describe a relationship to flour, rather than shares of a whole.
A small formula you can check yourself
Suppose a formula lists 500g flour, 350g water, 10g salt and 5g yeast. These are arithmetic examples, not a tested bread recipe.
| Ingredient | Weight | Baker’s percentage |
|---|---|---|
| Flour | 500g | 100% |
| Water | 350g | 70% |
| Salt | 10g | 2% |
| Yeast | 5g | 1% |
For each row, divide the ingredient weight by 500g and multiply by 100. The water calculation is 350 ÷ 500 × 100 = 70%. The total dough weighs 865g. Water’s share of that total is about 40.5%, which answers a different question.
Scale the weights, keep the relationships
If you want to use 750g flour instead, multiply every weight by 1.5. The new amounts are 750g flour, 525g water, 15g salt and 7.5g yeast. The dough is still 70% hydration because both flour and water increased together.
Working backward from a desired dough weight takes one more step. This example totals 173% of the flour weight. For 1,000g of dough, divide 1,000 by 1.73 to get about 578g flour. Multiply that flour amount by 0.70, 0.02 and 0.01 for the remaining ingredients. Round only after doing the calculations, so small rounding changes don’t accumulate.
Scaling ingredient weights doesn’t establish a new baking time. A smaller loaf or a different pan still needs the recipe’s relevant doneness checks.
Count the flour and water inside a starter
A sourdough starter contributes both ingredients. King Arthur’s hydration guide includes that contribution in the final calculation.
Imagine adding 100g starter made with equal weights of flour and water to 450g flour and 300g water. The starter brings 50g of each. Total flour is 500g; total water is 350g. The finished formula is therefore 70% hydration. Dividing only the separately added water by the separately added flour gives 66.7%, which misses the starter.
That equal split applies only when the starter itself has equal flour and water weights. Use the starter’s actual flour and water composition when it doesn’t.
What the number tells you while watching
Hydration gives you a clue about handling. A wetter dough may look slack and sticky even when the baker has measured correctly. Flour choice also changes how much water a dough can take, so two formulas with the same percentage needn’t feel identical.
Use the number to understand the baker’s task, then follow the complete recipe when you bake. Before changing a sticky dough, count all its flour and water and compare it with the recipe’s intended consistency. Adding flour by instinct changes the very ratio you’re trying to understand.