Sourdough Calculator
Baker's-percentage sourdough calculator with true hydration, recipe scaling and a levain build helper.
Set the recipe by
Levain breakdown:
Scale this recipe by
Levain build helper (ratio 1 : x : x, starter : flour : water)
How the baker's percentages work
Every ingredient is expressed as a percentage of flour weight (flour = 100%). Water = flour × hydration%, salt = flour × salt%, and levain = flour × levain%. Worked example: 1000 g flour at 75% hydration, 2% salt and 20% levain gives 750 g water, 20 g salt and 200 g levain, for a total dough weight of 1970 g. When you drive the calculator from a target total dough weight instead, it divides that target by (1 + hydration + salt% + levain%, as fractions) to back-solve the flour weight — 1970 g at those same percentages solves back to exactly 1000 g of flour.
Recipe hydration vs. effective hydration: "recipe hydration" is just the water you add divided by the flour you add (75% in the example). But your levain is itself part flour and part water — a 100%-hydration levain is half flour, half water by weight, so 200 g of levain contains 100 g flour and 100 g water. Effective hydration adds those hidden amounts in: (750 + 100) water ÷ (1000 + 100) flour = 850 ÷ 1100 ≈ 77.3%. A stiffer levain (lower levain hydration%) hides less water and effective hydration sits closer to recipe hydration; a very wet levain widens the gap.
Scaling and building levain
To scale a recipe, every ingredient is multiplied by the same factor — whether that factor comes from a target loaf count and weight, or a target total dough weight — so the baker's percentages never change. The levain build helper works out a 1:x:x build (equal parts flour and water, x times the starter) for any target amount: for a 200 g levain at 1:5:5, the 11 total parts split into roughly 18 g starter, 91 g flour and 91 g water.
Practical tips: professional bakers typically work in the 65–85% hydration range — below that the dough is stiff and easier to shape, above it you get a more open, irregular crumb but a stickier dough. Build your levain the night before with enough surplus for both your recipe and to keep your starter going, and always weigh ingredients in grams rather than volume for consistent results.
Sourdough Calculator: frequently asked questions
What is baker's percentage?
Baker's percentage expresses every ingredient as a percentage of the total flour weight (flour is always 100%). At 75% hydration and 2% salt, you use 75 g of water and 2 g of salt for every 100 g of flour, which makes recipes easy to scale to any size.
What is the difference between recipe hydration and effective hydration?
Recipe hydration is just the water you add divided by the flour you add. Effective (true) hydration also counts the flour and water already inside your levain, since a mature levain is itself part flour and part water — it gives a more accurate picture of how wet the final dough actually is.
How much levain should I use?
Most sourdough recipes use 15–25% levain (relative to flour weight). Less levain (10–15%) gives a longer, more flavourful fermentation; more levain (25%+) speeds things up but can taste less complex. 20% is a common starting point.
How do I scale my sourdough recipe up or down?
Keep every baker's percentage the same and multiply all four ingredient weights (flour, water, salt, levain) by the same scale factor. Use the scaling section to enter either the number of loaves or a target loaf weight and it recalculates every ingredient for you.
How do I build a levain from starter?
A 1:5:5 levain build means 1 part active starter to 5 parts flour to 5 parts water by weight, left to ripen until doubled and domed. The levain build helper works out the starter, flour and water needed to make any target amount at whatever ratio you choose.