How baker’s percentages work
In baker’s math the flour is always 100 percent, and every other ingredient is a share of the flour’s weight. A dough with 500 g of flour and 75 percent water has 375 g of water. This lets you scale a loaf up or down without touching the recipe: change the flour and everything else follows.
The idea and the notation are the ones in King Arthur Baking’s guide to baker’s percentage.
A 500 g loaf, worked out
With 500 g of flour, 75 percent water, 20 percent starter and 2 percent salt, the dough needs 375 g of water, 100 g of starter and 10 g of salt, and weighs 985 g.
| Flour | Water at 75% | Starter at 20% | Salt at 2% | Dough |
|---|---|---|---|---|
| 400 g | 300 g | 80 g | 8 g | 788 g |
| 500 g | 375 g | 100 g | 10 g | 985 g |
| 750 g | 562 g | 150 g | 15 g | 1478 g |
| 1000 g | 750 g | 200 g | 20 g | 1970 g |
What true hydration is
A starter is itself flour and water. The calculator takes it as equal weights of each, the usual way to keep one, so 100 g of starter brings 50 g of flour and 50 g of water into the dough. Counting those, the dough above holds 550 g of flour and 425 g of water, which is 77 percent hydration and not 75.
| Water | Starter | True hydration |
|---|---|---|
| 65% | 20% | 68% |
| 70% | 20% | 73% |
| 75% | 20% | 77% |
| 80% | 20% | 82% |
| 75% | 10% | 76% |
| 75% | 30% | 78% |
The difference matters when you compare recipes: one that says 75 percent may or may not count the starter.
Changing the numbers
More water gives a more open crumb and a stickier dough that is harder to shape.
More starter makes the dough rise faster. Less starter slows it down, which suits a long rise in a cool kitchen.
Salt stays close to 2 percent of the flour in most bread.
