Read the whole formula, not just the final bowl
Identify the flour basis before changing the batch size.
Start with what you actually weigh
A source recipe is a ledger of ingredients added to the final mix. Enter each weighed addition once. If the recipe calls for 100 g of ready levain, enter that 100 g as a preferment; do not also enter the flour and water that are already inside it as separate final-mix additions.
An original worked example
Imagine 450 g bread flour, 50 g wholemeal flour, 320 g water, 100 g of a 100%-hydration flour-and-water levain, and 11 g salt. The levain contains 50 g flour and 50 g water. Total flour is therefore 550 g, known water is 370 g and total dough is 931 g. The known-water hydration is 370 ÷ 550 × 100 = 67.27%.
The 500 g of flour poured directly into the bowl is not the whole flour basis. Dividing by 500 would miss the flour carried by the levain. The app's ingredient percentages use the full 550 g flour basis.
Use roles deliberately
Flour and water rows contribute their full mass to their respective totals. Preferment rows split into flour and water using your entered hydration. Everything else contributes mass, but no assumed water or flour. That means salt, seeds, milk and eggs belong in Other unless you have separately measured their components and intentionally model them elsewhere.
This limited model makes its assumptions inspectable. It does not try to estimate the water content of an egg or predict how a particular flour will feel. See the preferment arithmetic before changing a levain row.
Reference reading
For the general convention, see King Arthur Baking: Baker’s Percentage and its discussion of bread hydration. Worked examples and application explanations here are our own. No affiliation or endorsement is implied.