1. Understand the Basics of Hydration: Hydration in baking refers to the ratio of water to flour in your dough. It’s often expressed as a percentage, where the weight of water is divided by the weight of flour, then multiplied by 100. For example, if you have 100g of flour and 60g of water, your hydration is 60%.

2. Factor in Your Sourdough Starter: Your sourdough starter itself contains both flour and water (typically a 100% hydration starter has equal parts flour and water). When calculating total hydration for your dough, you must account for the flour and water contributed by the starter.

3. Consult the Hydration Chart for Bagels: A typical sourdough bagel dough has a lower hydration than many sourdough breads, usually ranging from 50% to 58%. This lower hydration is key to achieving that dense, chewy texture. The chart will provide specific weight ratios for flour, water, and starter to hit these percentages.

4. Calculate Your Dough’s Total Hydration: Using the chart, select your desired hydration percentage. Then, calculate the total flour and total water from both your main recipe ingredients and your starter. For instance, if your recipe calls for 500g bread flour, 250g water, and 100g of 100% hydration starter (which is 50g flour + 50g water), your total flour is 550g and total water is 300g. Your hydration would be (300/550) * 100 = ~54.5%.

5. Adjust Water or Flour to Meet Desired Hydration: If your initial calculation doesn’t match your target hydration from the chart, adjust either the water or flour incrementally. For a stiffer dough, reduce water or increase flour. For a slightly softer dough, increase water or reduce flour. Always make small adjustments.

6. Observe Your Dough’s Consistency: As you mix your dough, pay attention to its feel. A lower hydration bagel dough will be quite stiff and firm, not sticky. It should hold its shape well. This visual and tactile cue is crucial for confirming you’ve hit the right hydration.