How to use this calculator
Enter flour and water added to the bowl separately from the starter. Add the total starter mass and its own hydration percentage. The calculator separates that starter into flour and water before calculating the complete dough.
The formula
A worked example
500 g flour, 325 g water, and 100 g starter at 100% hydration contain 550 g total flour and 375 g total water. Final hydration is 68.18%.
Assumptions & limitations
Assumes the starter consists of flour and water only. Milk, eggs, butter, inclusions, and other sources of water are not modeled. This is a baker’s-percentage calculation, not a prediction of dough handling.
Common questions
Why is the answer higher than water divided by added flour?
The starter adds both flour and water. Their ratio can raise or lower the final hydration.
What is a 100% hydration starter?
It contains equal masses of flour and water, so a 100 g portion contains 50 g of each.
Supporting reference
The method above states this calculator’s assumptions. This reference provides related definitions and technical context.
King Arthur Baking: bread hydration ↗Formula and worked example checked against automated test cases. About our methodology.