Sourdough Calculator

What this does

So you want a sourdough loaf of a particular size and feel, and you would rather not do the baker's math by hand. This calculator builds the whole formula for you. You set your targets, the final dough weight, how wet you want it, how much salt and levain, and it works backwards to give you exact weights of flour, water, levain, and salt, plus a rough fermentation time.

How to use it

1. Enter the total weight of dough you want to bake.
2. Set your dough hydration, salt, levain, and levain hydration percentages.
3. Enter your proofing temperature, and the result updates with the full breakdown.

The defaults are a sensible everyday loaf, so you can tweak one number at a time and watch what changes.

What each input means

A quick tour, since the words matter here. Total dough weight is how much dough you want at the end, which sets the size of your loaf. Hydration is the water as a percentage of flour, the lever that decides how wet and open the crumb is. Salt is also a percentage of flour, usually around 2 percent for flavour and control. Levain is how much active starter you use, again as a percentage of flour. Levain hydration describes your starter itself, where 100 percent means equal weights of flour and water. Proofing temperature is how warm the dough will sit, which drives how fast it ferments.

How the maths works

It is all baker's percentage underneath. Since the dough is flour plus its water plus its salt, the tool first finds the flour by dividing the dough weight by everything built on top of it:

flour = total dough weight ÷ (1 + hydration + salt)

with hydration and salt written as decimals. From that flour weight it works out the salt and the levain, then splits the levain into its own flour and water using the levain hydration, and subtracts those from the totals so the final flour and water you add are correct. For an 800 gram loaf at 76 percent hydration and 2.1 percent salt, that lands at roughly 404 grams of flour, 297 grams of water, 90 grams of levain, and 9 grams of salt.

About the timing

The fermentation time is an estimate, not a stopwatch. The tool works it out from how much levain you used and how warm your proofing temperature is, since both speed up or slow down the rise. More levain and a warmer room mean a shorter time, less levain and a cooler room mean longer. Treat the number as a guide and watch the dough itself, because your flour, your starter's vigour, and your kitchen all have a say. The dough is ready when it has risen well and looks alive, whatever the clock says.

Questions people ask

References

1. King Arthur Baking. Hydration in Bread Dough, Explained. https://www.kingarthurbaking.com/blog/2023/01/11/bread-hydration
2. King Arthur Baking. Baker's Percentage. https://www.kingarthurbaking.com/pro/reference/bakers-percentage