Most home recipes are written as a shopping list: 500 g flour, 350 g water, 10 g salt. Baker's percentage, also called baker's math or formula percentage, rewrites that list as ratios to the flour. The numbers add up to well over 100, which looks strange at first, but it is the most useful habit a bread baker can pick up. It lets you scale a recipe to any size, compare two recipes at a glance, spot a typo before it ruins a batch and make deliberate changes instead of guesses. This guide covers the rule, conversions in both directions, how preferments and sourdough fit in, and the mistakes that trip people up.
The one rule: everything is relative to the flour
In baker's percentage the total weight of flour is always 100%. Every other ingredient is expressed as a percentage of that flour weight:
ingredient % = ingredient weight ÷ total flour weight × 100
A dough with 1,000 g flour and 700 g water is therefore a 70% hydration dough, and 20 g of salt in it is 2% salt. The percentages describe relationships between ingredients, not shares of the finished dough. Water at 70% does not mean the dough is 70% water; it means there are 70 g of water for every 100 g of flour.
Why flour? It is the largest ingredient in nearly every bread, and it is the ingredient everything else acts on. Water hydrates it, salt tightens its gluten and yeast feeds on its starches. Anchoring the formula to flour makes each number meaningful on its own: a baker who reads "2% salt" knows the bread is normally seasoned, whereas "10 g salt" tells you nothing until you know the size of the batch.
Multiple flours add up to 100%
When a formula uses more than one flour, the flours together make 100%. A loaf with 400 g bread flour and 100 g whole wheat flour has 500 g total flour, so it is 80% bread flour and 20% whole wheat. Rye, spelt, einkorn, semolina and other milled grains all count as flour. Things that are not flour, such as seeds, rolled oats, cooked grains, cocoa powder or cheese, are still written as a percentage of the flour, but they sit outside the 100%.
The same rule works outside bread. Cookies, cakes and brownies have no water and lots of sugar and fat, so their percentages add up to 400–700% — see baker's percentages for cookies, cakes and brownies.
Converting a recipe in grams to percentages
Here is a simple same-day loaf with a little whole wheat. Start by adding up the flours (425 + 75 = 500 g), then divide every ingredient by that total:
| Ingredient | Weight | Calculation | Baker's % |
|---|---|---|---|
| Bread flour | 425 g | 425 ÷ 500 × 100 | 85% |
| Whole wheat flour | 75 g | 75 ÷ 500 × 100 | 15% |
| Water | 360 g | 360 ÷ 500 × 100 | 72% |
| Salt | 10 g | 10 ÷ 500 × 100 | 2% |
| Instant yeast | 3 g | 3 ÷ 500 × 100 | 0.6% |
| Total | 873 g | 174.6% |
The bottom line, 174.6%, is the total percentage, sometimes called the formula yield. It is the number that makes scaling possible. Notice that 873 g of dough divided by 500 g of flour is 1.746, the same figure written as a decimal. That makes a handy self-check: if the percentages do not add up to the dough weight divided by the flour weight, something has been mis-copied.
Converting percentages to grams for any dough weight
Once a formula is in percentages you can make exactly as much dough as you need. Divide the target dough weight by the total percentage (as a decimal) to find the flour, then multiply the flour by each ingredient's percentage:
total flour = target dough weight ÷ (sum of percentages ÷ 100)
Suppose you want a single 1,000 g loaf from the formula above. 1,000 ÷ 1.746 = 572.7 g of flour. Then:
- Bread flour: 572.7 × 0.85 = 486.8 g
- Whole wheat flour: 572.7 × 0.15 = 85.9 g
- Water: 572.7 × 0.72 = 412.4 g
- Salt: 572.7 × 0.02 = 11.5 g
- Instant yeast: 572.7 × 0.006 = 3.4 g
Those amounts add back up to 1,000 g. This is exactly the arithmetic the baker's percentage calculator on our home page does, and the guide to scaling bread recipes covers multiple loaves, pizza balls and allowances for dough lost to the bowl.
Total formula vs final dough
Things get slightly more involved when part of the flour and water is fermented ahead of time in a preferment: a poolish, biga, sponge or sourdough levain. Bakers describe the same bread in two ways.
The total formula counts every gram of flour and water in the bread, including what is inside the preferment. It is the version you use to judge the bread: its true hydration, true salt level and so on. The final dough is what you actually weigh on mixing day: the ripe preferment plus the remaining flour, water and other ingredients.
Take a sourdough with 1,000 g total flour, 750 g total water and 20 g salt, where 200 g of levain at 100% hydration (100 g flour plus 100 g water) is built the night before:
| Ingredient | Total formula | Baker's % | Final dough |
|---|---|---|---|
| Flour | 1,000 g | 100% | 900 g |
| Water | 750 g | 75% | 650 g |
| Salt | 20 g | 2% | 20 g |
| Ripe levain (100 g flour + 100 g water) | already counted above | — | 200 g |
| Total | 1,770 g | 177% | 1,770 g |
Calculate percentages from the final dough alone and you would get 650 ÷ 900 = 72.2% hydration and 2.2% salt. Both are wrong: the levain's flour and water belong to the bread too, so the real hydration is 75% and the real salt is 2%. This is the convention used in the Bread Bakers Guild of America's formula format and in most professional baking textbooks, and it is why sourdough hydration is quoted for the total formula. The share of the total flour that has been fermented in advance, here 100 ÷ 1,000 = 10%, is called the prefermented flour (PFF). Our guide to sourdough hydration explains PFF and stiff starters in detail.
Typical ranges
These ranges cover most breads home bakers make. A number far outside them is not necessarily wrong, but it is worth a second look before you mix.
| Ingredient | Typical baker's % | Notes |
|---|---|---|
| Salt | 1.8–2.2% | 2% is the default for lean bread; much below 1.5% tastes flat |
| Instant yeast | 0.1–2% | Low end for long or cold fermentation, 1–2% for fast same-day doughs |
| Active dry yeast | 0.13–2.5% | 1.25 × the instant yeast amount |
| Fresh yeast | 0.3–6% | 3 × the instant yeast amount |
| Sourdough levain | 10–30% | Levain weight as a percentage of total flour |
| Water: bagels and pretzels | 50–60% | Stiff dough, tight and chewy crumb |
| Water: sandwich loaves | 60–65% | Soft, easy to shape |
| Water: baguettes | 65–72% | Supple, moderately open crumb |
| Water: country sourdough | 70–80% | Soft, open, glossy crumb |
| Water: ciabatta and focaccia | 75–90% | Very slack, large irregular holes |
| Sugar | 0–15% | None in lean breads; enriched loaves usually 5–15% |
| Butter or oil | 0–60% | Sandwich loaves 3–10%; brioche 30–60% or more |
See the bread hydration chart for hydration by bread type, and the yeast conversion guide for swapping fresh, active dry, instant yeast and sourdough starter.
Common mistakes
- Using the dough weight as the base. Percentages are of the flour, not of the whole dough. The 10 g of salt in the 873 g dough above is 2% of the 500 g of flour. Dividing by the dough weight gives 1.1%, which would make you think the bread is under-salted.
- Forgetting hidden flour. Starter, poolish, biga and a cooked flour paste such as tangzhong all contain flour that belongs in the 100%.
- Counting the levain twice. If the levain's flour and water are already included in the total flour and water, do not also add the levain percentage to the sum when you scale.
- Treating milk, eggs and butter as water. Milk is about 87% water, whole eggs about 75% and butter about 16%. A dough made with 300 g of milk is not as wet as one made with 300 g of water.
- Measuring by volume. Baker's math only works with weights. Depending on how it is filled, a cup of all-purpose flour can weigh anywhere from about 120 g to 150 g.
- Rounding too early. Round only the final gram amounts, never the flour weight in the middle of the calculation, and weigh yeast and salt on a scale that reads to 0.1 g if you can.