How to use it
Decide how much dough you want and the percentages you want to bake at. The calculator gives the grams to weigh out. All percentages are of total flour, which includes the flour inside your starter, so the hydration you choose is the hydration you get.
Baker's percentages in one paragraph
Bakers write recipes with flour as 100% and every other ingredient as a percentage of it. A 75% hydration, 2% salt, 20% starter loaf can be scaled to any size without rewriting anything, and two recipes can be compared at a glance. The catch with sourdough is that the starter contains flour and water too, which is why this calculator solves for the flour and water you add after the starter's share is taken out.
Worked example. One 1,000 g loaf at 75% hydration, 20% starter (100% hydration) and 2% salt.
Total flour = 1,000 ÷ (1 + 0.75 + 0.02) = 565 g. Total water = 565 × 0.75 = 424 g. Starter = 565 × 0.20 = 113 g, which holds 56.5 g flour and 56.5 g water.
So you weigh out 508 g flour, 367 g water, 113 g starter and 11 g salt, and the four add back up to 1,000 g.
The formula
Total flour = dough weight ÷ (1 + hydration + salt)
Starter = total flour × starter %
Flour to add = total flour − flour in starter
Water to add = total flour × hydration − water in starter
Salt = total flour × salt %
Choosing the numbers
- Hydration. If you are new to a flour, start around 70% and raise it a few points per bake. The hydration calculator explains what each range feels like.
- Starter. More starter means a faster rise. Lower amounts, such as 10%, slow fermentation down, which can suit a warm kitchen or an overnight bulk.
- Salt. Around 2% of total flour is the common standard for bread.
Limits of this calculator
- Expect to lose a few grams to the bowl and bench, so scale up slightly if loaf weight matters.
- Add-ins (seeds, fruit, cheese) are not included in the dough weight here.
- If the starter alone holds more water than your chosen hydration allows, the calculator will say so instead of giving negative water.