How to Calculate Sourdough Hydration: Baker’s Percentages
By The Calcumatix Team Reviewed by Calcumatix Editorial Review 4 min read
Quick Answer
Hydration percentage equals water weight divided by flour weight, multiplied by 100: Hydration % = (Water ÷ Flour) × 100. For 375 g of water and 500 g of flour: 375 ÷ 500 × 100 = 75 percent hydration. If your recipe includes a sourdough starter, split the starter into its flour and water components first, add them to the main recipe totals, then calculate true hydration from the combined figures.
Sourdough hydration is the weight of water in a dough expressed as a percentage of the total flour weight. Bakers express it this way, rather than as a ratio of water to total dough weight, because keeping flour at 100 percent makes every other ingredient easy to scale up or down without recalculating the entire recipe. A 75 percent hydration dough has 75 grams of water for every 100 grams of flour. The calculation uses weight, never volume: flour is too compressible for cup measurements to be consistent across bakers or even across the same baker on different days.
How Do You Calculate Sourdough Hydration Step by Step?
- Weigh all ingredients in grams (flour is 100%).
- Sum total recipe flour and total recipe water.
- Split sourdough starter into flour and water components and add to totals to find true hydration.
Working The Hydration Percentage Step By Step
Step 1, Weigh all ingredients in grams. Sourdough hydration is always calculated by weight. A kitchen scale accurate to 1 gram is required. The recipe should list flour, water, salt, and starter all in grams.
Step 2, Identify the total flour weight. In baker’s percentages, flour is always the baseline (100%). Sum all flour types in the recipe: if the recipe uses 400 g bread flour and 100 g whole wheat flour, the total flour weight is 500 g.
Step 3, Identify the total water weight. Count only the water added directly to the dough at this stage. Do not yet include water inside the starter.
Step 4, Calculate basic hydration. Hydration % = (Water weight ÷ Total flour weight) × 100
Step 5, Account for the starter (for true hydration). Sourdough starter is a mixture of flour and water. A 100 percent hydration starter (equal parts flour and water by weight) contains 50 percent flour and 50 percent water. To find true dough hydration, add the flour and water from the starter to your running totals before calculating.
Step 6, Calculate true hydration. True Hydration % = (Total water including starter water ÷ Total flour including starter flour) × 100
Sourdough Hydration Worked Example
Recipe: 500 g bread flour, 350 g water, 100 g sourdough starter (100% hydration), 10 g salt.
Step 1: Split the starter into flour and water A 100 g portion of 100% hydration starter = 50 g flour + 50 g water.
Step 2: Calculate total flour Total flour = 500 g (recipe flour) + 50 g (from starter) = 550 g
Step 3: Calculate total water Total water = 350 g (recipe water) + 50 g (from starter) = 400 g
Step 4: Calculate simple hydration (flour and water only, no starter) Simple Hydration = (350 ÷ 500) × 100 = 70%
Step 5: Calculate true hydration (including starter contributions) True Hydration = (400 ÷ 550) × 100 = 72.7% (rounded to one decimal place)
Result: The dough has a simple hydration of 70 percent and a true hydration of 72.7 percent. Most sourdough discussion uses simple hydration, but true hydration is more accurate when comparing doughs from different recipes with different starter quantities.
Use the sourdough hydration calculator to adjust water ratios and scale recipes easily.
What Do Different Hydration Levels Mean for the Dough?
Hydration percentage directly affects how the dough feels and how the finished loaf behaves.
| Hydration | Feel | Typical Result |
|---|---|---|
| 60 to 65% | Stiff, smooth, easy to handle | Denser crumb, great for beginners and sandwich loaves |
| 70 to 75% | Soft but workable, some stickiness | Moderate open crumb, versatile, forgiving |
| 78 to 82% | Wet and slack, requires stretch-and-fold technique | Open crumb, ear development, more complex to handle |
| 85%+ | Very slack, barely holds shape without cold retard | Large, irregular holes, requires experience and a Dutch oven |
Higher hydration produces a more open crumb (larger, more irregular air pockets) because water converts to steam in the oven and the wetter gluten network stretches further around the gas bubbles. It does not automatically produce a better loaf: the right hydration is the one that matches your flour’s protein content, your ambient temperature, and your shaping skill.
How Do Baker’s Percentages Let You Scale a Recipe?
Because every ingredient is expressed as a percentage of flour, scaling a recipe is simple multiplication. Decide how much total dough you want, divide by the sum of all percentages expressed as decimals, and that gives you the flour weight. Then multiply each percentage by the flour weight to find each ingredient’s weight.
Scaling worked example: The recipe above has percentages: flour 100%, water 70%, starter 20%, salt 2% (salt is 10 g ÷ 500 g = 2%). Sum of percentages as decimals = 1.00 + 0.70 + 0.20 + 0.02 = 1.92. To make 960 g of dough: flour = 960 ÷ 1.92 = 500 g, water = 500 × 0.70 = 350 g, starter = 500 × 0.20 = 100 g, salt = 500 × 0.02 = 10 g.
Sources
- The Perfect Loaf: Understanding Baker’s Percentages, baker’s math, hydration calculation, and scaling method for sourdough.
- Sourdough Pedia: Hydration Formula Explained, simple vs. true hydration, starter flour/water split.
See all baking and kitchen measurement tools in the maths calculators hub.
Frequently asked questions
Why Do I Have to Use Grams Instead of Cups?
A cup of flour can vary from 120 g to 160 g depending on how it is scooped and whether the flour has settled. A gram is always a gram. Hydration percentages are meaningless unless the weights are accurate. Invest in a digital scale: it is the single most effective tool for consistent sourdough baking.
What Hydration Should I Start With as a Beginner?
Start at 70 to 72 percent hydration. The dough is workable without extensive wet-dough handling technique. Once you can successfully shape and score a 70 percent dough and achieve a good rise, move to 75 to 78 percent and learn the stretch-and-fold technique required at higher hydrations. Jumping straight to 80-plus percent is a common beginner frustration.
Does Whole Wheat Flour Change the Hydration Calculation?
The formula stays the same, but whole wheat flour absorbs more water than white bread flour because of the bran content. A recipe formulated at 75 percent hydration with white flour will feel noticeably stiffer if you substitute whole wheat flour without increasing water. When substituting whole wheat flour for part of the recipe flour, increase the water by approximately 1 to 2 percent of the flour weight for each 10 percent of whole wheat substituted.
How Do I Calculate the Hydration of My Starter?
Starter hydration = (Starter water weight ÷ Starter flour weight) × 100. A starter fed equal parts flour and water by weight is a 100 percent hydration starter. A starter fed 1 part water to 2 parts flour by weight is a 50 percent hydration (stiff) starter. The starter’s hydration determines how much water it contributes to the dough when you include it in the true hydration calculation.