What Is Baker's Percentage? A Visual Guide for Sourdough Bakers
If you have ever read a sourdough recipe that listed ingredients as percentages — flour 100%, water 75%, salt 2% — and wondered how a recipe can add up to more than 100%, you have met baker’s percentage. It looks strange at first, then becomes the only sane way to write down bread.
Here is the whole idea in one sentence: the flour is always 100%, and every other ingredient is expressed as a percentage of that flour weight. That is it. Once that clicks, every formula you read for the rest of your baking life gets easier.
The one rule: flour is always 100%
Most measuring systems anchor to the total — the way a nutrition label adds up to 100% of the whole. Baker’s percentage does the opposite. It anchors to the flour, because flour is what everything else reacts with: water hydrates it, salt seasons and tightens it, starter ferments it.
So the percentages are not parts of a whole. They are ratios to the flour:
- Flour = 100% (by definition, always)
- Water = (water weight ÷ flour weight) × 100
- Salt = (salt weight ÷ flour weight) × 100
- Starter = (starter weight ÷ flour weight) × 100
This is why the numbers happily climb past 100%. A dough at “75% hydration” simply means the water weighs 75% of what the flour weighs. The total formula can sum to 180%, 190%, more — and that is correct, not a typo.
A worked example: a 75% hydration loaf
Let’s build a single loaf from a clean 500 g of flour. Hydration is 75%, starter is 20%, salt is the classic 2%. Watch how each gram comes straight out of the flour weight:
| Ingredient | Baker’s % | The math | Grams |
|---|---|---|---|
| Flour | 100% | the anchor | 500 g |
| Water | 75% | 0.75 × 500 | 375 g |
| Starter | 20% | 0.20 × 500 | 100 g |
| Salt | 2% | 0.02 × 500 | 10 g |
| Total dough | 197% | sum of the above | 985 g |
Every number on the right is just the flour weight (500 g) multiplied by the percentage. Nothing else. If your flour weight changes, you re-run the same four multiplications and you have a new recipe — same bread, different size.
Notice the total: 197%. That is the sum of all the percentages, and it is the key to scaling, which we will get to in a moment.
Why bakers actually use it
Percentages are not academic flourish. They solve two real problems.
1. Scaling to any size, instantly. Say you want a bigger batch — a target dough weight of 1,500 g instead of 985 g. You do not guess. You divide the target by the total percentage (as a decimal):
Flour needed = 1,500 g ÷ 1.97 = 762 g
Then re-apply the same percentages to that new flour weight: water 75% → 571 g, starter 20% → 152 g, salt 2% → 15 g. Add them up and you land back on ~1,500 g of dough at the exact same hydration and seasoning. The bread is identical; only the loaf count changed.
2. Comparing recipes at a glance. Two recipes written in grams tell you almost nothing — one might be a boule, one a baguette batch. But written as percentages, they line up instantly. A 70% hydration dough is tighter and easier to shape; an 85% dough is slack, open, and ciabatta-like. The moment you read in percentages, you can predict how a dough will handle before you touch it. That shared language is why every professional formula, every bread book, and every serious baking forum speaks in baker’s percentage.
A note on starter (and “true” hydration)
Here is the nuance most calculators quietly ignore: your starter is itself flour and water. A 100 g starter built at 100% hydration is really 50 g flour + 50 g water. So the dough above does not actually contain 500 g of flour and 375 g of water — it contains:
- True flour: 500 + 50 = 550 g
- True water: 375 + 50 = 425 g
- True total hydration: 425 ÷ 550 = ~77%
Both numbers are useful. The 75% formula hydration is what you dial in and compare against other recipes. The ~77% true hydration is what your dough actually feels like in the hands. Knowing the gap keeps you from being surprised when a “75%” dough handles a little wetter than expected — and it is exactly the calculation our calculator does for you automatically.
Quick reference: common percentages
Once you internalize the anchor, these become second nature:
- Hydration 65–70% — beginner-friendly, holds shape, easy scoring.
- Hydration 72–78% — the everyday sourdough range; open crumb, still manageable.
- Hydration 80%+ — high-hydration, dramatic holes, needs confident handling.
- Salt 1.8–2.2% — standard. Below this tastes flat; above it slows fermentation.
- Starter 15–25% — typical inoculation. More starter = faster bulk; less = slower, more sour.
That is the entire system. Flour is 100%, everything else is measured against it, and the total percentage is your scaling key. Write your recipes this way once and you will never go back to a pile of disconnected gram weights.