Why bakers write recipes as percentages
A home recipe says "500 g flour, 350 g water". A bakery formula says "100% flour, 70% water" — and that second version survives contact with reality. It scales from one loaf to fifty without recalculating anything, it lets you compare two recipes at a glance (is this dough wetter than the one I made last week?), and it makes the levers explicit: hydration, salt and yeast each become a single number you can reason about.
The rule is simply: every ingredient ÷ total flour × 100, and flour is always 100%. That's why the column adds up past 100 — the percentages aren't slices of the dough, they're ratios to the flour. Our basic lean loaf totalling 171% means the dough weighs 1.71× its flour, which is exactly the number you divide by when scaling to a target batch.
Three example formulas
These are our own illustrative starting points, not copies of a published recipe. Each is shown at 500 g of flour, computed by the calculator's engine. For comparison, King Arthur Baking's published white bread is 66% water, its two ciabattas 73% and 82%, and its brioche 50% butter and 50% eggs.
Lean white loaf — 171% total, 855 g of dough
| Ingredient | Baker's % | At 500 g flour |
|---|---|---|
| Bread flour | 100% | 500 g |
| Water | 68% | 340 g |
| Salt | 2% | 10 g |
| Instant yeast | 1% | 5 g |
Rustic country-style loaf — 181% total, 903 g of dough
| Ingredient | Baker's % | At 500 g flour |
|---|---|---|
| Bread flour | 90% | 450 g |
| Whole wheat flour | 10% | 50 g |
| Water | 78% | 390 g |
| Salt | 2% | 10 g |
| Instant yeast | 0.6% | 3 g |
Lightly enriched soft dough — 190% total, 951 g of dough
| Ingredient | Baker's % | At 500 g flour |
|---|---|---|
| Bread flour | 100% | 500 g |
| Milk | 55% | 275 g |
| Butter | 12% | 60 g |
| Sugar | 10% | 50 g |
| Egg | 10% | 50 g |
| Salt | 2% | 10 g |
| Instant yeast | 1.2% | 6 g |
Scaling to the batch you actually want
Three questions come up, and the calculator answers all of them. "I have this much flour" is the simple direction — multiply through. "I want this much dough" runs backwards: divide the target by the formula's total percentage, because dough weight = flour × total%. "I want N loaves of this size" is the same calculation with the target computed for you. Some dough always stays in the bowl and on the bench, so if your loaves must hit an exact weight, add a little to the target.
Where percentages need care
- Multiple flours share the 100%. With 90% bread flour and 10% whole wheat, the 100% is their sum — so a 78% hydration is measured against all the flour, not just the white.
- A sourdough starter hides flour and water. List it as its own ingredient, not as flour. Its flour and water still change the dough's true hydration: ignore them and the figure reads low with a typical 100% starter, or high with a stiff one. The sourdough hydration calculator splits it correctly.
- Not every ingredient's water is counted. Our hydration figure counts plain liquids such as water and milk. Eggs and butter carry water too, but only partly, so they're left to your judgement rather than quietly guessed.
- Percentages don't scale technique. A 3× batch needs the same fermentation judgement and a bigger bowl; the numbers scale, the dough's behaviour doesn't always follow.
Changing yeast type as well as batch size? The yeast converter handles fresh, active dry and instant, and the cups to grams converter turns a volume-measured recipe into the weights this calculator needs.
Sources
- King Arthur Baking, Baker's percentage: flour is always 100%, a preferment is treated as any other ingredient, and the white bread, French bread and 73% ciabatta formulas.
- King Arthur Baking, What is baker's math?: every flour counts toward the total, salt at 1.8–2.2%, and the 82% ciabatta and brioche formulas.