Understanding baker’s percentage
Why bakers express every ingredient as a percentage of the flour weight, and what that makes possible.
The question this answers
What is baker’s percentage, and why does every professional formula use it?
The convention
In baker’s percentage, the total flour in a formula is defined as 100 per cent, and every other ingredient is expressed as a percentage of that flour weight.
So a dough with 1,000 g of flour, 700 g of water, 20 g of salt and 10 g of yeast is described as 100 per cent flour, 70 per cent water, 2 per cent salt, 1 per cent yeast. The percentages add up to more than 100, which is the part that surprises people first and stops mattering almost immediately.
Why it is worth the initial confusion
Three things become easy that are otherwise awkward.
Scaling is arithmetic rather than judgement: to make half as much, halve the flour and apply the same percentages. Comparing formulas becomes possible at a glance, because 70 per cent hydration means the same thing in any recipe regardless of batch size. And the numbers themselves become meaningful — an experienced baker reads '2 per cent salt’ and knows immediately whether it is normal, because they have read that number hundreds of times.
None of this works with volume measures or with absolute weights alone.
Where it gets subtle
Two points cause most of the confusion.
When a formula uses more than one flour, they are added together to make the 100 per cent. Rye at 20 per cent and white at 80 per cent sum to the flour total, and every other percentage is calculated against that sum.
When a preferment or a starter is used, the flour and water inside it count toward the formula’s totals. A hydration figure that ignores the water in a levain understates the dough’s real hydration, sometimes substantially. This is the single most common error in published sourdough formulas and it is why two recipes claiming the same hydration can produce visibly different doughs.
What it does not tell you
Baker’s percentage describes proportions and says nothing about process. Two doughs at identical percentages, one fermented warm for four hours and one cold for eighteen, are different breads.
It also says nothing about the flour. Seventy per cent hydration in a strong white flour and 70 per cent in a wholemeal are not comparable doughs, because the flours absorb differently. The number is a common language, not a specification.
Related
Covers
The guide explains the convention; the calculator applies it and shows its working.
Hydration is the percentage bakers reach for first, and the one most often misstated when a levain is not counted.
Apply this with a tool
The guide names counting the levain as the commonest error in published sourdough formulas; the calculator does that arithmetic.