Science

Baker's percentages, explained simply

A recipe says “500 g flour, 350 g water, 100 g starter, 10 g salt”. A formula says “flour 100, water 70, levain 20, salt 2”. They describe the same bread. The second one also describes every other size of that bread, and it can be compared with any other formula in the world at a glance.

The one rule

Flour is 100. Everything else is a share of the flour.

Ingredient	Weight	Percentage
Flour	1,000 g	100
Water	720 g	72
Levain	200 g	20
Salt	20 g	2

To get a percentage, divide the ingredient by the flour and multiply by 100. To get a weight back, multiply the flour by the percentage and divide by 100. That is the whole method.

Why bakers bother

Three reasons, and each one saves a mistake.

Scaling. Need forty loaves instead of four? Multiply the flour by ten and every other line follows, because every line is tied to the flour. Scaling a recipe written in grams by hand is where salt gets doubled and water gets forgotten.

Reading. Once you know the ranges, a formula tells you what the dough will be like before you touch it. Water at 65 is a firm dough for tins and rolls. Water at 75 is most sourdough. Water at 82 needs strong flour and a confident hand. Salt sits at 2, almost always. Levain at 20 ferments faster than levain at 10.

Comparing. Two loaves that look alike in a book can be told apart in two numbers. A formula with 78 water and 15 levain and one with 70 water and 25 levain are different breads, and you know how before baking either.

The levain question

The levain has flour and water of its own. Some bakers count only the main flour as 100 and write the levain as one line, as in the table above. Others fold the levain’s flour and water into the totals. The first way is simpler to write. The second gives the true water share of the dough. Both are fine. Write on the sheet which one you used, because a hydration number without that note has cost more than one bakery a bad morning.

Several flours

When the flour is a blend, the blend is 100. A dough with 800 g white and 200 g wholemeal is written as white 80, wholemeal 20. Change the blend and the water usually changes with it; more wholemeal means the dough wants more water.

Keep it round

One decimal at most. Salt at 2.0 or 2.2 is a real choice. Salt at 2.04 is noise; a bakery scale reads to the gram, and the flour absorbs differently from week to week by more than that.

Write every recipe this way once, and the rest of the bakery’s arithmetic, from the bake list to the flour order, becomes something a machine can do for you.

Questions bakers ask

How do you calculate baker's percentage?

Divide the ingredient's weight by the flour's weight and multiply by 100. With 1,000 g flour and 720 g water, water is 72 percent. Flour itself is always 100.

Why is flour always 100 percent?

Because every other ingredient is measured against it. That is what lets the same formula describe a batch of two loaves and a batch of two hundred.

What does 75 percent hydration mean?

That the water weighs three quarters of the flour. 750 g of water for every 1,000 g of flour. It says nothing about the total weight of the dough.

Related

• Flour protein content for bread: what the number means and what to buy. Bread flour runs 11.5 to 13.5 percent protein; under 11 is pastry, over 14 suits enriched doughs and long fermentations. Protein quality matters as much as the number.
• What is autolyse, and how long should it be?. Autolyse is a rest of flour and water only, 20 minutes to an hour for most doughs, before salt and leaven go in. It shortens mixing and makes dough extensible.
• Bakery production planning: when a spreadsheet stops being enough. A spreadsheet plans a bakery well up to about fifteen products and a few standing orders. Past that, the bake list, mixing sheet and stock start to disagree.

Sources: Hamelman, Bread, 3rd ed.; Suas, Advanced Bread and Pastry; Bread Bakers Guild of America, Formula Formatting Guidelines. Updated 2026-09-11.