Sourdough Calculator

The Sourdough Calculator helps you create precise recipes for sourdough bread by calculating exact ingredient weights based on baker's percentages. Unlike commercial yeast recipes, sourdough bread uses a live culture (starter) that contributes both flour and water to your dough — this calculator automatically accounts for the starter's contribution to get your target hydration exactly right.

Whether you're baking a classic country loaf, an open-crumb artisan boule, or a hearty whole wheat bread, simply enter your desired loaf weight, hydration level, and starter percentage to get a complete recipe with gram-precise measurements.

At a Glance

Sourdough Calculator turns loaf count, loaf weight, hydration, starter percentage and salt into gram weights for flour, water, starter and salt. It also builds a baking timeline adjusted to kitchen temperature.

Sourdough Calculator: features at a glance

Feature	What you get	Good for
Recipe inputs	Set the number of loaves, loaf weight, hydration, starter percentage, starter hydration, salt percentage and kitchen temperature.	Scaling a formula to the loaves you plan to bake
Starter accounted for	The starter is split into its flour and water, so added flour and water are shown separately and the target hydration holds.	Hitting 72% or 78% hydration with a live starter
Baker's percentages	Shows each ingredient as a percentage of total flour, with flour at 100%, plus the starter's flour and water contribution.	Comparing formulas and scaling them up or down
Flour type	Choose bread flour, all-purpose, whole wheat, spelt or rye to see notes on each flour's protein content.	Switching between white and whole-grain loaves
Baking timeline	A step-by-step schedule runs from starter feeding through autolyse, bulk fermentation, shaping and baking, with times adjusted to your kitchen temperature.	Planning when to start so the loaf is ready on time
Preset styles	Quick Example buttons load settings for styles such as Classic Country at 72% hydration and High Hydration at 78%.	Starting from a familiar loaf style

How to Use the Sourdough Calculator

Step 1: Choose a Preset or Customize

Click a Quick Example button to load settings for popular sourdough styles like Classic Country (72% hydration) or High Hydration (78%). Or enter your own values for a fully custom recipe.

Step 2: Set Your Flour Type and Kitchen Temperature

Choose your flour type — bread flour, all-purpose, whole wheat, spelt, or rye — for relevant protein content notes. Enter your kitchen temperature so the calculator can estimate accurate bulk fermentation and proofing times.

Step 3: Click Calculate Recipe

Click the Calculate Recipe button to generate your complete recipe with exact weights for flour, water, starter, and salt.

Step 4: Follow the Baking Timeline

Use the step-by-step timeline — from starter feeding through autolyse, bulk fermentation, shaping, and baking — with temperature-adjusted time estimates for each phase.

Step 5: Review the Starter Breakdown

Check how your starter's flour and water contributions factor into the recipe. The breakdown shows exactly what the starter adds so you understand the true baker's percentages of your dough.

Understanding Baker's Percentages in Sourdough

Baker's percentages express each ingredient as a percentage of the total flour weight. Flour is always 100%. In sourdough, the starter itself contains flour and water, so the calculator decomposes the starter into its components. For a 100% hydration starter, half of its weight is flour and half is water.

For example, in a recipe with 500g total flour, 20% starter (100g), and 72% hydration (360g water): the starter contributes 50g flour and 50g water. So you'd add 450g flour and 310g water separately.

How Kitchen Temperature Affects Fermentation

Temperature is the primary factor controlling sourdough fermentation speed. Yeast and bacteria activity roughly doubles with every 8-10°C increase. At a warm 28°C (82°F), bulk fermentation might finish in 3-4 hours. At a cool 18°C (64°F), it could take 8-12 hours. The calculator estimates timing based on your kitchen temperature, starter percentage, and hydration to give you a practical baking schedule.

Hydration Levels Explained

Low hydration (50-60%): Stiff dough, easy to shape. Used for bagels and pretzels.
Medium hydration (65-72%): Balanced and versatile. Perfect for sandwich loaves and standard sourdough.
Medium-high hydration (73-80%): Soft, extensible dough with open crumb and large holes.
High hydration (80-100%): Very wet and slack. Produces ciabatta-style bread with dramatic open crumb structure.

Frequently Asked Questions

What is hydration in sourdough bread?

Hydration is the ratio of total water to total flour in the dough, expressed as a percentage. A 72% hydration dough has 72 grams of water for every 100 grams of flour. This includes water and flour contributed by the sourdough starter. Higher hydration (75-85%) produces more open crumb with larger holes, while lower hydration (60-68%) creates a tighter, more uniform crumb.

What is baker's percentage and how does it work?

Baker's percentage expresses each ingredient as a percentage of the total flour weight. Flour is always 100%. For example, 72% hydration means 72g water per 100g flour, and 20% starter means 20g starter per 100g flour. This system makes it easy to scale recipes to any size while keeping ratios consistent.

How does sourdough starter contribute to the recipe?

Sourdough starter is a mixture of flour and water containing wild yeast and bacteria. A 100% hydration starter (equal parts flour and water by weight) contributes both flour and water to your dough. The calculator decomposes the starter into its flour and water components to calculate how much additional flour and water you need to add separately.

How does temperature affect sourdough fermentation?

Temperature is the most important factor controlling fermentation speed. Yeast activity roughly doubles with every 8-10 degrees Celsius increase. At 24°C (75°F), bulk fermentation typically takes 4-6 hours. At 18°C (64°F), it may take 8-12 hours. The calculator adjusts timing estimates based on your kitchen temperature.

What is the ideal starter percentage for sourdough?

Most sourdough recipes use 15-25% starter (baker's percentage). A 20% starter is a good default that balances flavor development and reasonable timing. Lower percentages (10-15%) give a milder flavor and longer fermentation for more complex taste. Higher percentages (25-40%) speed up fermentation and produce a more sour flavor.

What is autolyse and why is it important?

Autolyse is the process of mixing flour and water and letting them rest for 30-60 minutes before adding starter and salt. During this rest, flour fully hydrates and gluten bonds begin forming naturally. This results in better gluten development, improved dough extensibility, and a more open crumb structure with less kneading effort.

How do I scale a sourdough recipe from one loaf to two?

If the loaves are the same size and you want the same dough, double each ingredient weight while keeping the hydration, starter percentage, and salt percentage unchanged. For example, a recipe using 500 grams of flour, 100 grams of starter, and 10 grams of salt becomes 1,000 grams of flour, 200 grams of starter, and 20 grams of salt. Check that your mixing bowl and proofing containers can handle the larger batch.

Why is the added flour amount smaller than the total flour in a sourdough recipe?

The starter already contains flour as well as water, so a recipe may show less added flour than the total flour used to calculate its ratios. For example, 100 grams of 100% hydration starter contains about 50 grams of flour and 50 grams of water. If a formula targets 500 grams of total flour, about 450 grams may be added separately, with the rest coming from the starter.

Can I use a different hydration starter without changing the recipe?

Changing starter hydration changes how much flour and water the starter contributes, even when its total weight stays the same. For instance, 100 grams of a 100% hydration starter contains about 50 grams each of flour and water; a stiffer starter contributes a different split. Enter your starter’s actual hydration so the recipe can account for its flour and water when calculating the additions.