Sourdough Calculator - Flour, Water, Starter, and Salt
Use this free sourdough calculator to convert a flour weight and baker's percentages into the exact flour, water, starter, salt, total dough weight, and total hydration for your sourdough loaf.
Sourdough Calculator
Results
What Is Sourdough Calculator?
A sourdough calculator turns a single flour weight and a handful of baker's percentages into the ingredient list, total dough weight, and total hydration for a sourdough loaf. Enter the flour weight, the water, starter, and salt percentages, and the starter hydration, and the calculator returns the grams of flour, water, starter, and salt, plus the total hydration that includes the water carried inside the starter.
- • Plan a New Loaf: Set the flour weight to match the loaf size and the calculator applies the standard 100% flour, 67% water, 20% starter, 2% salt ratios.
- • Adjust Hydration: Move the water percentage up to 80% for an open crumb or down to 65% for a tighter, easier-to-shape dough.
- • Scale Up for Multiple Loaves: Increase the flour weight and the calculator returns the full ingredient list, including the flour and water carried in the levain.
- • Test Starter Hydration: Compare a 100% hydration levain against a stiff 50% starter to see how the levain changes the dough's total hydration.
Sourdough baking is a numbers problem in disguise, so most home bakers reach for a calculator once they start adjusting ratios. The Omni Calculator, King Arthur Baking, and The Perfect Loaf all use the same baker's percentage backbone.
For bakers who want to build the formula from raw percentages before they enter a flour weight, our baker's percentage calculator turns any flour weight into ingredient grams using the same 100% flour backbone.
How Sourdough Calculator Works
The calculator applies the standard sourdough baker's percentage, where every ingredient is a percentage of the total flour weight. The starter splits into its own flour and water using the user-entered starter hydration, so the final total hydration reflects the water carried inside the levain, not just the added water on top.
- Total Flour: The 100% anchor the user enters. Every other ingredient weight is a percentage of this value.
- Water Percentage: Added water as a percentage of flour weight. 67% is the Omni default; 70-80% gives a more open crumb.
- Starter Percentage: Levain weight as a percentage of flour weight. 20% is standard; warmer kitchens often use 15% and cooler kitchens 25%.
- Salt Percentage: Salt weight as a percentage of flour weight. The standard sourdough ratio is 2%.
- Starter Hydration: Water-to-flour ratio inside the starter itself. A 100% hydration starter uses equal weights of flour and water.
- Total Hydration: Total water (added plus the water inside the starter) divided by total flour (flour plus the flour inside the starter), expressed as a percentage.
The math runs through the user-entered flour weight, so you scale the formula by changing only the flour input and leave the four percentages alone, which is the simplest way to bake a different number of loaves from the same base recipe.
Worked Example: 500 g Loaf at 70% Hydration
Flour = 500 g, Water = 70%, Starter = 20%, Salt = 2%, Starter Hydration = 100%
1. Added water = 500 x 70 / 100 = 350 g. 2. Starter = 500 x 20 / 100 = 100 g, split into 50 g flour and 50 g water. 3. Salt = 500 x 2 / 100 = 10 g. 4. Total flour = 500 + 50 = 550 g, total water = 350 + 50 = 400 g. 5. Total hydration = 400 / 550 x 100 = 72.7%. 6. Total dough = 550 + 400 + 10 = 960 g, or about 1.3 loaves at 750 g each.
Flour 500 g, Water 350 g, Starter 100 g, Salt 10 g, Total dough 960 g, Total hydration 72.7%, Loaves 1.3.
This is the everyday home sourdough formula, and it shows how a 70% added-water loaf lands at about 73% total hydration once the starter's own water is included.
According to Omni Calculator - Sourdough, the sourdough baker's percentage uses 100% flour, 67% water, 20% starter, and 2% salt by default, and total hydration equals total water divided by total flour times 100.
If you would rather work in cups, tablespoons, or fluid ounces for the added water, the cooking measurement converter translates the gram-based water line of the formula into kitchen-friendly volume units.
Key Concepts Explained
Four ideas make sourdough math easier once you start adjusting ratios:
Baker's Percentage
Every ingredient is a percentage of the total flour weight, so flour is always 100% and water, starter, and salt sit near 70%, 20%, and 2%. The same formula scales from a 200 g test bake to a 2 kg batch.
Total Hydration vs Added Water
Added water is the percentage you type into the calculator, while total hydration also includes the water carried inside the starter. A 70% added-water loaf with a 100% hydration 20% starter lands near 72.7% total hydration.
Starter Hydration
The water-to-flour ratio inside the levain. A 100% hydration starter uses equal weights of flour and water, a 50% starter carries more flour, and a 125% starter carries more water than flour.
Levain Flour and Water
Every gram of starter adds some flour and some water to the final dough, and the split depends on the starter hydration. The calculator shows starter flour and starter water separately so you can see how the levain shifts the totals.
Keeping these four ideas in mind prevents under-hydrating the dough and forgetting that the starter counts toward the total flour and water.
For a closer look at how flour weight shifts between cups, tablespoons, and grams depending on the brand, the ingredient volume to weight converter explains the density reasoning behind the total flour line of this calculator.
How to Use This Calculator
Follow these six steps to turn a flour weight into a complete sourdough formula:
- 1 Enter the Total Flour Weight: Type the total flour in grams. 500 g is a good default for one home loaf, 1000 g covers two loaves, and 200 g works for a small test bake.
- 2 Set the Water Percentage: Pick the added water as a percentage of flour weight. 67% is the Omni default, 70% is a comfortable middle, and 80% gives a wetter crumb.
- 3 Set the Starter Percentage: Pick the levain as a percentage of flour weight. 20% is standard; cooler kitchens often push to 25% to keep fermentation on schedule.
- 4 Set the Salt Percentage: Pick salt as a percentage of flour weight. Most sourdough recipes sit at 2%, and sweet enriched doughs sometimes drop to 1.5%.
- 5 Set the Starter Hydration: Enter the water-to-flour ratio inside the starter. 100% is the most common, stiff levain lives at 50-60%, and liquid levain sits at 110-125%.
- 6 Read the Results and Scale: Use the four ingredient weights, total dough, and total hydration to mix and time the dough. The loaves line shows whether the batch is one, two, or three loaves at 750 g each.
For example, with 500 g flour, 70% water, 20% starter, 2% salt, and 100% starter hydration, the calculator returns 350 g added water, 100 g starter, 10 g salt, a 960 g total dough, and 72.7% total hydration, which is the standard 1.3-loaf home bake.
If you keep a backup jar of active dry yeast for a yeasted sourdough blend, the yeast conversion calculator covers the fresh-to-dried yeast ratio you can use alongside the levain.
Benefits of Using This Calculator
Using a dedicated sourdough calculator gives you several practical benefits over a paper recipe:
- • Adjust Ratios Without Re-Math: Change the water, starter, or salt percentage and the ingredient weights and total hydration update in real time.
- • Total Hydration Includes the Starter: See the hydration that actually matters, including the water carried inside the levain, not just the added-water percentage.
- • Loaf Count Built In: The loaves line divides the total dough by the 750 g per loaf benchmark from King Arthur Baking.
- • Scale the Formula Safely: Multiply the flour weight by the number of loaves you want to bake and the rest of the percentages follow.
- • Compare Starter Hydrations: Toggle the starter hydration between 50%, 100%, and 125% to see how the levain shifts the total flour, water, and hydration.
- • Plan Cost and Storage: Knowing the exact grams makes it easier to feed the right amount of starter, store the dough, and budget the bake.
Most home bakers use the calculator a few times per bake, especially when switching between a single loaf, a double batch for the freezer, or a stiff levain for a rye blend.
When you turn the leftover starter into a sourdough pizza, the pizza dough calculator applies a similar baker's percentage system to the dough so the same flour weight workflow works for the next meal.
Factors That Affect Your Results
A few real-world factors change how you should read the calculator result:
Kitchen Temperature
A 20% starter at 24 C ferments faster than at 19 C, so cool kitchens often push the starter percentage to 25% to keep the bulk rise on schedule.
Flour Type
Whole wheat and rye flours absorb more water than bread flour, so the same 70% added-water formula feels stiffer in a whole grain loaf. Bump the water percentage by 5 points for high-extraction flours.
Starter Maturity
A young starter that has just been fed peaks faster than a fully mature starter, so the same 20% levain can ferment 30-60 minutes faster than expected. Watch the dough, not the clock.
Salt Preference
Some bakers prefer 1.8% salt for a milder loaf and others push to 2.2% for a more savory profile. The calculator accepts the full 0-4% range, so the salt line stays in step with the rest of the formula.
- • The calculator assumes the user-entered flour weight is the only flour source, so high-percentage rye or whole wheat blends can shift the actual total flour by a few grams.
- • It does not account for water absorbed by add-ins like seeds, oats, or dried fruit, so a 20% seed inclusion will need roughly 5 percentage points more added water to keep the dough workable.
These factors are small for most home bakes, but they matter when you scale a sourdough formula for a bakery, switch flour blends, or chase a specific open-crumb look.
According to King Arthur Baking - Sourdough Recipes, a standard home sourdough loaf is shaped around 750 g of dough, which the calculator uses to translate a batch weight into a count of loaves.
Once you have the exact flour, water, starter, and salt weights, the recipe cost calculator multiplies the grams by your pantry prices so you can see the cost per loaf alongside the hydration.
Frequently Asked Questions
Q: How much starter do I need for 500 g of flour in sourdough?
A: At the standard 20% levain, you need 100 g of starter for 500 g of flour. Bump the starter to 25% in a cool kitchen and the calculator returns 125 g of starter for the same 500 g of flour.
Q: What hydration should sourdough be?
A: Most home sourdough sits between 70% and 80% total hydration. Beginners usually do well at 70-72%, open-crumb loaves push 78-80%, and bagel-style dough drops below 65% for a denser crumb.
Q: How do you calculate sourdough hydration with starter?
A: Total hydration equals total water (added water plus water inside the starter) divided by total flour (flour plus flour inside the starter), multiplied by 100. A 70% added-water loaf with a 100% hydration 20% starter lands near 72.7% total hydration.
Q: How much salt do I add per 100 g of flour for sourdough?
A: The standard sourdough ratio is 2% salt, so 2 g of salt per 100 g of flour. Sweet or low-sodium bakers often drop to 1.5% (1.5 g per 100 g), while very savory loaves can push to 2.5% (2.5 g per 100 g).
Q: What is the baker's percentage for sourdough bread?
A: The classic sourdough baker's percentage is 100% flour, 67% water, 20% starter, and 2% salt. The Omni Calculator, King Arthur Baking, and most home recipes use these same numbers as a starting point.
Q: How much flour and water are in a 100% hydration sourdough starter?
A: A 100% hydration starter uses equal weights of flour and water. So 100 g of starter carries 50 g of flour and 50 g of water, while 200 g of starter carries 100 g of flour and 100 g of water.