Baker’s percentages state every ingredient as a percentage of the flour weight, so flour is always 100 per cent and everything else is measured against it. A 500 g flour dough at 75 per cent hydration needs 375 g of total water — and if 20 per cent starter at 100 per cent hydration is going in, that starter already contributes 50 g, so only 325 g is added directly.
That last step is where most hydration calculations go wrong: the water in the starter is water, and counting it twice or not at all both produce a dough that is not the one you intended.
What does hydration actually do?
It sets both handling and crumb, and the two move together across a fairly narrow range.
| Hydration | Handling | Crumb |
|---|---|---|
| Below 65% | Stiff, kneads easily | Tight and even |
| 70–75% | Workable, slightly tacky | Open, irregular |
| 80%+ | Slack, needs coil folds | Very open, needs a banneton |
Past about 80 per cent the dough stops responding to kneading and wants coil folds instead, and it needs support during the final proof or it spreads. That is a technique change rather than a difficulty setting, which is why jumping straight to a high hydration usually produces a flat loaf rather than an open one.
Flour matters as much as the number. A strong bread flour absorbs more water than a plain one, and wholemeal more again, so 75 per cent on one flour handles like 70 on another.
How is pizza dough different?
Lower hydration, higher salt, and a longer cold ferment. Neapolitan dough runs at 58 to 62 per cent, and a home oven benefits from around 65 because it cannot reach the temperature a wood oven does and the extra water buys a little more oven spring.
Six hundred grams of flour at 62 per cent takes 372 g of water and 15 g of salt, which makes roughly four 250 g dough balls.
Pizza is salted harder than bread — 2.5 to 3 per cent against 2 — because the dough is thin and eaten with strongly flavoured toppings. Salt also slows fermentation, which is useful when a dough is going to sit in the fridge for two days.
What else is a percentage?
Everything in the formula. Salt at 2 per cent of flour, yeast at 0.5 to 1 for a commercial-yeast dough, starter at 15 to 25 for a sourdough, and any oil, sugar or milk on the same basis.
Written out, a straightforward sourdough is five numbers: flour 100, water 75, starter 20, salt 2, and a fermentation schedule. That is the whole recipe, it fits on a line, and it scales to any batch size by choosing a flour weight — which is why professional bakeries write formulas rather than recipes.
Why state everything against the flour?
Because it makes doughs comparable regardless of size. A recipe at 500 g of flour and one at 5 kg have the same percentages, so a formula scales without any arithmetic beyond multiplying the flour.
It also makes the levers visible. Salt at 2 per cent, yeast at 0.5, hydration at 75 — those three numbers describe a dough completely, and changing one of them is a single, legible adjustment rather than a rewritten ingredient list.
The convention is why professional formulas are written this way and why a home recipe expressed in cups cannot be compared with anything.
What does the starter contribute?
Flour and water in whatever proportion it was fed at, and both have to be counted. A 100 per cent hydration starter is equal parts flour and water by weight, so 100 g of it is 50 g of flour and 50 g of water.
That means the starter changes the total flour as well as the total water. At 20 per cent starter on 500 g of flour, the 100 g of starter adds 50 g of flour — so the true flour total is 550 g and the true hydration is calculated against that, not against the 500 g in the ingredient list.
Whether to include starter flour in the denominator is a genuine convention difference between bakers. What matters is being consistent, because a formula that switches convention halfway produces a dough that does not match either reading.
Questions people ask
Does higher hydration always mean a more open crumb? It helps and it is not sufficient. Fermentation, shaping and oven heat all contribute, and a slack dough handled badly gives a dense loaf with large irregular holes rather than an open even crumb.
How much salt? Around 2 per cent of flour weight for bread and 2.5 to 3 for pizza. Below about 1.5 the dough ferments too fast and the loaf tastes flat.
Why is my dough stickier than the percentage suggests? Usually the flour. Protein content and milling both change absorption, and a percentage that works with one bag can be 5 points too high with another.
Can I convert a cup recipe into percentages? Only approximately, because the cup weights are estimates. Weighing the ingredients once as you make it converts the recipe permanently and accurately.
What hydration should a beginner start at? Around 68 to 70 per cent with a strong bread flour. It is workable by hand, forgiving of imperfect shaping, and close enough to the open-crumb range that the result is worth eating while the technique is still arriving.
Work in percentages against the flour, count the starter’s water, and change one lever at a time. The sourdough hydration calculator handles the starter contribution, and the pizza dough hydration calculator sizes dough balls at a target hydration and salt level.