The idea
In baker's percentages, the total flour in a recipe is always 100%. Every other ingredient is written as a percentage of that flour weight. So a dough with 1,000 g of flour and 700 g of water is 70% water, usually called 70% hydration.
Because the percentages refer to flour rather than the total, they do not add up to 100. A typical lean sourdough adds up to around 195 to 200%.
The two formulas you need
- Percentage = ingredient weight ÷ flour weight × 100
- Weight = flour weight × percentage ÷ 100
For 500 g of flour at 75% hydration: 500 × 75 ÷ 100 = 375 g of water. For 2% salt: 500 × 2 ÷ 100 = 10 g.
A worked example
| Ingredient | Weight | Baker's % |
|---|---|---|
| Bread flour | 450 g | 90% |
| Whole wheat flour | 50 g | 10% |
| Water | 375 g | 75% |
| Levain (100% hydration) | 100 g | 20% |
| Salt | 10 g | 2% |
| Total dough | 985 g | 197% |
The two flours together make the 100%: 90% bread flour and 10% whole wheat. Water is 75%, levain 20% and salt 2%. The total, 197%, is useful for scaling.
Our convention: levain on top
There are two common ways to treat the starter. On this site, percentages are calculated against the flour you add to the bowl, and the levain is listed as its own line. This is how most home recipes are written and it keeps the numbers simple.
The levain also contains flour and water, though. A 100 g levain at 100% hydration holds 50 g flour and 50 g water. Counting those in gives the overall hydration:
| Flour | Water | Hydration | |
|---|---|---|---|
| Added to the bowl | 500 g | 375 g | 75% |
| From the levain | 50 g | 50 g | - |
| Overall | 550 g | 425 g | about 77% |
When you compare recipes from different sources, check which convention each uses. A recipe that says 80% overall hydration may feel very similar to one that says 75% with 20% levain on top.
Scaling a recipe
To make a dough of a particular total weight, divide that weight by the total percentage to find the flour, then work out everything else.
- Choose the dough weight. Two 900 g loaves need 1,800 g of dough. Add 2 to 3% for losses in the bowl: about 1,850 g.
- Find the flour. 1,850 ÷ 1.97 = about 939 g. Round to 940 g.
- Multiply out. Water 75% = 705 g. Levain 20% = 188 g. Salt 2% = 18.8 g, call it 19 g.
The calculator does this arithmetic for you.
Typical ranges
| Ingredient | Usual range | Notes |
|---|---|---|
| Water | 60 to 90% | Sandwich loaves at the low end, focaccia at the high end. Wholegrain flour absorbs more. |
| Levain | 10 to 25% | Less levain means a longer, slower bulk ferment. |
| Salt | 1.8 to 2.2% | 2% is standard. Below about 1.5% bread tastes flat and ferments fast. |
| Fat | 0 to 10% | Butter or oil softens crumb and crust. |
| Sugar or honey | 0 to 6% | Adds softness and browning in tin loaves. |
Why it is worth learning
With percentages you can see at a glance that one recipe is wetter than another, halve or triple any recipe without errors, and change one thing at a time when you experiment. When a loaf goes wrong, the troubleshooting guide often points to one of these numbers.