Sourdough Calculator

Work out the exact water, salt, and total dough weight for a sourdough loaf from baker's percentages — accounting for the flour and water already in your starter.

Quick Facts

Method
Baker's percentages: total flour = 100%
Water and salt are figured against total flour, including the flour in your starter.

Your Recipe

Calculated
Water to add
-
Beyond the water in your starter
Salt to add
-
Weighed, not by volume
Starter to add
-
Ripe, active levain
Total dough weight
-
Flour + water + salt

Ready

Enter your flour, hydration, starter, and salt, then calculate.

How the sourdough calculator works

Sourdough recipes are built on baker's percentages: total flour is the 100% baseline, and every other ingredient is expressed as a percentage of that flour weight. This is why bakers can scale a formula up or down without re-testing it — the ratios stay fixed even as the absolute weights change. The one wrinkle that trips people up is the starter (levain): it is itself flour and water, so it must be counted toward both the total flour and the total water before the numbers work out.

The formula

Given the flour you add to the bowl, a target hydration, a starter amount, your starter's own hydration, and a salt percentage, the calculator does the following:

  • Starter weight = bowl flour x (starter % / 100). At the default 500 g flour and 20% starter, that is 100 g of starter.
  • Split the starter into flour and water using its hydration. A 100% hydration starter is equal parts flour and water: starter flour = starter / (1 + starter hydration/100). For 100 g at 100%, that is 50 g flour and 50 g water.
  • Total flour = bowl flour + starter flour = 500 + 50 = 550 g. This is the 100% baseline.
  • Total water = total flour x (hydration / 100) = 550 x 0.75 = 412.5 g. Water to add = total water − water already in the starter = 412.5 − 50 = 362.5 g.
  • Salt = total flour x (salt % / 100) = 550 x 0.02 = 11 g.
  • Total dough weight = total flour + total water + salt = 550 + 412.5 + 11 = 973.5 g.

Salt and hydration are both figured against total flour, not just the flour you scooped into the bowl. Skipping the starter's flour is the single most common mistake, and it makes doughs run a few percent wetter and slightly under-salted.

Common reference points

  • Hydration: 65-70% is beginner-friendly and holds its shape; 70-75% is a classic country loaf; 80%+ gives an open, airy crumb but sticky, harder-to-handle dough.
  • Salt: almost always 1.8-2.2% of total flour. Below ~1.5% the loaf tastes flat and ferments too fast; above ~2.5% it slows the yeast noticeably.
  • Starter: 15-25% of flour is typical. More starter ferments faster (shorter bulk); less starter ferments slower (better for overnight retards).
  • Starter hydration: a "1:1" liquid starter is 100%; a stiff starter or sweet levain may be 50-60%.

Frequently Asked Questions

Why does the calculator add the starter's flour to the total?
Baker's percentages are only consistent if 100% means all the flour in the dough. Your starter is roughly half flour by weight (for a 100% hydration starter), and that flour absorbs water and carries salt just like the flour you added directly. Counting it keeps hydration and salt percentages honest — otherwise a dough you think is 75% hydration would actually be a bit wetter.
What hydration should I use?
Start at 70% if you are new to sourdough — it is forgiving to shape. A 75% country loaf is the everyday standard. Push toward 80-85% for an open, holey crumb once your shaping is confident. Whole-grain and rye flours drink more water, so raise hydration 5-10% when you swap them in.
How much salt does sourdough need?
2% of total flour is the reliable default. Salt tightens the gluten and slows fermentation, so cutting it makes a slack, fast-proofing dough; too much stalls the rise. Weigh salt rather than using teaspoons — fine sea salt and coarse kosher salt have very different densities per spoon.
My starter is stiff, not 100% hydration. Does that matter?
Yes, and the calculator handles it. Set the "Starter hydration" field to your actual value (for example 60% for a stiff levain). A stiffer starter carries less water and more flour per gram, so the water-to-add figure rises accordingly.

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