Start with a formula you can read both ways
| Ingredient in the final mix | Weight | Percentage of 500 g added flour |
|---|---|---|
| Added flour | 500 g | 100% |
| Added water | 350 g | 70% |
| Starter at 100% hydration | 100 g | 20% |
| Salt | 10 g | 2% |
| Total dough | 960 g | 192% |
The total is 192% because the denominator is the flour alone. This convention makes a final mix easy to weigh. The starter’s percentage is its full 100 g divided by the 500 g flour you add at mixing. It is a convenient description of the formula’s ingredient lines.
Include the starter when comparing total formulas
The 100 g of equal-weight starter contains 50 g flour and 50 g water. The same dough contains 550 g flour and 400 g water in total. On that denominator, total hydration is 72.7% and salt is about 1.82%. Prefermented flour is 50 ÷ 550, or about 9.1%. That figure describes the flour that arrived already fermented. It answers a different question from the 20% starter weight in the final-mix table. [2]
| Question you are answering | Calculation for this dough |
|---|---|
| How much starter do I weigh? | 20% of 500 g added flour gives 100 g. |
| What is the total hydration? | 400 g total water ÷ 550 g total flour = 72.7%. |
| How much flour is prefermented? | 50 g starter flour ÷ 550 g total flour = 9.1%. |
Do the conversion once. If the recipe’s total flour already includes the levain, adding the levain flour again makes the denominator too large. If the build uses a stiff starter, the starter split formula gives the correct amount to add.
Go from percentages to grams
Choose a flour weight and convert each percentage to a decimal before multiplying. To use the final-mix table with 600 g added flour, multiply 600 by 0.70 for 420 g water, by 0.20 for 120 g starter and by 0.02 for 12 g salt. The new dough weighs 1,152 g. Keep the starter at the same hydration for that conversion. [1]
If you are aiming for a specific dough weight, divide that weight by 1.92 to find the added flour weight for this convention. For example, 1,056 g ÷ 1.92 gives 550 g added flour. The ingredient amounts become 550 g flour, 385 g water, 110 g starter and 11 g salt. If the scale rounds small amounts, keep the rounding visible. [1]
Crispy Crust’s planned formula view would show the gram weights and their percentage convention side by side. That could help you spot a changed denominator before you copy a formula into your next bake.
Combine flours without losing the denominator
If the 500 g of added flour is made from 400 g white and 100 g whole wheat, write those as 80% and 20% on the added-flour denominator. They add to 100%. Water and salt percentages still use the combined 500 g. For a total-flour comparison, include the type of flour in the starter too. With a 50 g white-flour contribution, this dough has 100 g whole wheat out of 550 g total flour, or 18.2%. Label both lines if you will use them for different jobs. This also makes comparisons easier.
Check the sourdough hydration calculator to include the flour and water in your starter without counting them twice.