Sourdough Hydration Calculator
Enter your flour, water and starter to get the dough's true hydration percentage.
Hydration is the weight of water as a percentage of the weight of flour. For sourdough, you must include the flour and water inside your starter. With a 100%-hydration starter (equal flour and water), half its weight is flour and half is water, which are added to the totals before dividing water by flour.
How to Use This Calculator
Enter the flour and water you add to the dough, plus the weight of your starter. The calculator assumes a 100%-hydration starter — equal parts flour and water by weight, the most common kind — and splits it accordingly before working out the true hydration.
Hydration drives how a dough handles and bakes: higher hydration gives a more open, airy crumb but a stickier, harder-to-shape dough; lower hydration is stiffer and easier to handle.
How the Calculation Works
Hydration is baker's percentage for water: the water weight divided by the flour weight, times 100. The catch with sourdough is that the starter is itself flour and water, so ignoring it understates the real hydration.
For a 100%-hydration starter, half its weight is flour and half is water. The calculator adds those halves to your flour and water totals, then divides total water by total flour.
hydration = (water + starter/2) ÷ (flour + starter/2) × 100
Worked Example
With 500 g flour, 350 g water and 100 g of 100%-hydration starter: the starter contributes 50 g flour and 50 g water. Total flour is 550 g and total water is 400 g.
Hydration is 400 ÷ 550 × 100 = 72.7%, a touch higher than the 70% you'd get ignoring the starter.
Assumptions and Limitations
- Assumes a 100%-hydration starter (equal flour and water)
- Counts the starter's flour and water in the totals
- Excludes salt and add-ins, which aren't part of hydration
- For a stiffer or liquid starter, adjust the flour/water split
Who Uses a Sourdough Hydration Calculator
Home and hobby bakers use this to find a dough's hydration percentage from the flour, water, and starter. Run it to dial in a recipe, compare formulas, or troubleshoot a dough that is too wet or stiff. Enter your ingredient weights to get the hydration and totals.
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Open calculator →Frequently Asked Questions
How do you calculate sourdough hydration?
Divide total water by total flour and multiply by 100, including the flour and water in your starter. For a 100% starter, half its weight counts as each.
Why include the starter in hydration?
Because the starter is made of flour and water, leaving it out understates the dough's real hydration. Counting it gives the accurate figure that affects handling and crumb.
What is a good hydration for sourdough?
Beginners often start around 65–70%, which is manageable. Higher hydrations of 75–85% give a more open crumb but are stickier and trickier to shape.
What does 100% hydration starter mean?
A starter fed with equal weights of flour and water. So 100 g of it is 50 g flour and 50 g water — the split this calculator uses by default.
Does salt count toward hydration?
No. Hydration is only water relative to flour. Salt, oil and other add-ins are calculated as their own baker's percentages, separate from hydration.
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