Have you ever followed a sourdough recipe to a T, only to end up with a dough that’s either a sticky, unmanageable puddle or a tough, dense brick? The culprit is often a misunderstood concept: hydration. And the most common mistake? Forgetting to account for your sourdough starter.
Accurate hydration is the secret sauce to consistent, bakery-quality loaves. Whether you’re chasing that wild, open crumb or a sturdy sandwich loaf, understanding how to calculate it properly—starter and all—is a game-changer.
Let’s break down the math, banish the confusion, and get you on the path to sourdough mastery.
What is Sourdough Hydration, Anyway?
In the world of baker’s math, hydration is simply the ratio of total water to total flour in your dough, expressed as a percentage.
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Higher Hydration (75%+): Leads to a more open, airy crumb with large holes and a thinner, crispier crust. The dough is stickier and trickier to handle. Think artisan country loaves.
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Lower Hydration (60-70%): Results in a tighter, more uniform crumb and a thicker, chewier crust. The dough is firmer and easier to shape. Perfect for beginners or sandwich bread.
The “Hidden” Water and Flour: Why Your Starter Matters
Here’s where many bakers go wrong. They calculate hydration based only on the flour and water they add from the bag and tap. But your sourdough starter is also made of flour and water!
If you add 100g of starter to your dough, you aren’t just adding “100g of starter.” You are adding a specific amount of flour and a specific amount of water. Ignoring this can throw your final hydration off by several percentage points, which is a huge difference in the world of bread.
The Golden Formula
To get the true hydration percentage of your dough, you need to use this formula:
Hydration % = (Total Water ÷ Total Flour) x 100
Where:
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Total Water = Water in your recipe + Water in your starter
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Total Flour = Flour in your recipe + Flour in your starter
Your Step-by-Step “Calculator” Guide
Let’s walk through a practical example. Most home bakers maintain their starter at 100% hydration, which means it’s fed with equal weights of flour and water. This makes the math super easy.
Let’s assume you have a recipe with these ingredients:
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450g Bread Flour
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300g Water
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100g Sourdough Starter (at 100% hydration)
Step 1: Break Down Your Starter
Since your 100g starter is at 100% hydration, it’s made of exactly half flour and half water.
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Flour in starter: 50g
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Water in starter: 50g
Step 2: Calculate Total Flour
Add the flour from the recipe to the flour from the starter.
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450g (recipe) + 50g (starter) = 500g Total Flour
Step 3: Calculate Total Water
Add the water from the recipe to the water from the starter.
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300g (recipe) + 50g (starter) = 350g Total Water
Step 4: Do the Division
Now, plug your totals into the main formula.
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(350g Total Water ÷ 500g Total Flour) = 0.7
Step 5: Convert to a Percentage
Multiply by 100 to get your final hydration %.
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0.7 x 100 = 70% Hydration
So, the true hydration of this dough is 70%, a perfect “sweet spot” for everyday baking that balances ease of handling with a lovely crumb.
What if My Starter Isn’t 100% Hydration?
No problem! The principle is the same, the math just takes an extra step. Let’s say you have a stiff starter kept at 60% hydration.
If you have 100g of this stiff starter, you need to figure out its parts.
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Total Parts: 100 (flour) + 60 (water) = 160 parts.
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Flour amount: (100 / 160) * 100g starter = 62.5g flour
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Water amount: (60 / 160) * 100g starter = 37.5g water
You would then use these numbers in Steps 2 and 3 above.
Final Tips for Success
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Start Low: If you’re new to sourdough, aim for a final hydration of roughly 65-70%. It’s much more forgiving to practice shaping with a firmer dough.
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Increase Gradually: Once you’re comfortable, bump up the hydration by 2-3% at a time. Don’t jump straight from 65% to 85%!
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Flour Matters: Whole grain flours absorb more water than white flour. A 75% hydration dough made with significant whole wheat will feel stiffer than the same dough made with all white flour.
By taking the extra minute to calculate your true hydration, you’re taking control of your baking. No more guessing games—just consistent, delicious results. Happy baking!