Sourdough & Baker’s Percentage Calculator
Reverse loaf scaling, true starter hydration, and bulk fermentation timing.
Baking Formulation2 Loaves (850 g each)
Precise weights ready for kitchen scales
True Total Hydration: 77.3%
Your recipe calls for 75% added water. But because your 173 g sourdough starter contributes 86 g water and 86 g flour, your true overall dough hydration is 77.3%.
Bulk Fermentation Timing Assistant
Estimated fermentation duration based on kitchen ambient temperature
Visual Dough Readiness Cues (Always watch dough, not the clock)
- ✓Target dough volume rise: approximately 60% (do not wait for 100% doubling)
- ✓Surface is slightly domed with smooth, semi-translucent skin
- ✓Visible small fermentation bubbles underneath surface and along container walls
- ✓Gentle bowl shake reveals a soft, aerated, gelatinous jiggle
- ✓Dough releases cleanly from container edges when tipped
How Baker’s Percentage Works
Standard culinary recipes list ingredients in volumetric cups or grams that are tied to a fixed batch size. In professional baking, this makes scaling awkward and recipe comparisons impossible.
Baker’s math solves this by standardizing the total weight of flour to exactly 100%. Every other ingredient is measured and expressed as a proportion of that flour weight:
Because flour is always 100%, the total percentage of all ingredients will always exceed 100% (in the example above, 197%). This is completely normal and is what allows bakers to scale formulas up to 100 loaves or down to a single roll without recalculating from scratch.
Why Reverse Loaf Scaling Matters
Most online calculators force you to guess an arbitrary starting flour weight (like 500g or 1,000g). But home bakers have physical constraints: your banneton proofing baskets and Dutch ovens are designed for specific dough volumes—typically 750g, 850g, or 900g per loaf.
If you start with 1,000g of flour at 75% hydration and 20% starter, you end up with 1,970g of dough. When you divide that into two loaves, each weighs 985g—which may overflow an 8-inch round banneton or touch the Dutch oven lid.
BakerPercent’s reverse scaling lets you specify your target output (for example, 2 loaves at 850g each = 1,700g total dough). The calculator uses:
You get zero wasted dough and perfectly portioned loaves every single bake.
Understanding True Total Hydration
A standard active sourdough starter (levain) is maintained at 100% hydration, meaning it contains equal parts flour and water by weight (a 1:1 ratio).
When a recipe calls for 200g of starter, that starter introduces 100g of water and 100g of flour to the mixing bowl. If your base recipe called for 700g of water on 1,000g of flour (70% added hydration), your actual total wetness is:
Beginners often wonder why their dough feels wetter than expected. BakerPercent shows added-water hydration and true total hydration separately so you can adjust the recipe with both figures in view.
Temperature & Bulk Fermentation Kinetics
Commercial bakeries control dough temperatures with proofing cabinets set to 78°F (25°C). Home kitchens, however, fluctuate with the seasons. A recipe written for a 78°F kitchen that advises “bulk ferment for 4 hours” will leave your dough severely underproofed in a 66°F (19°C) winter kitchen, or hopelessly overproofed on an 82°F (28°C) summer afternoon.
Sluggish yeast activity. Expect 7 to 9 hours of bulk fermentation. Aim for a 75% volume rise before shaping.
Balanced yeast and bacterial acid production. Expect 4.5 to 5.5 hours. Aim for a 55–65% volume rise.
Rapid fermentation. Can finish in under 3.5 hours. Shape early at 40–50% rise to prevent gluten breakdown.
Frequently Asked Questions
What is baker's percentage and how does it work?▼
In baker's percentages (or baker's math), total flour weight is always defined as 100%. Every other ingredient (water, sourdough starter, salt) is measured and expressed as a percentage relative to that flour weight. This allows recipes to be scaled instantly for any batch size.
What is the difference between added water hydration and true total hydration?▼
Added water hydration only measures the liquid poured directly into the mixing bowl relative to dry flour. True total hydration includes both the water and flour contained inside your sourdough starter (which is typically 50% water and 50% flour by weight). BakerPercent calculates both so you can see your dough's total hydration.
How much sourdough starter should I use in my bread recipe?▼
Standard artisan sourdough recipes typically use 15% to 20% starter relative to total flour weight. For a long, slow overnight bulk fermentation in cool kitchens, 10% to 15% is recommended. In warm kitchens (above 78°F / 25°C), reducing starter inoculation prevents overproofing.
How do I calculate ingredients backward from my desired loaf weight?▼
Divide your desired total dough weight by the sum of all baker's percentages (Flour 100% + Hydration % + Starter % + Salt %). For example, if you want a 900g loaf at 75% hydration, 20% starter, and 2% salt, divide 900 by 1.97 to get ~457g of base flour.
How does ambient room temperature affect bulk fermentation?▼
Wild yeast and lactic acid bacteria ferment significantly faster in warm environments. At 75°F (24°C), bulk fermentation typically takes 4.5 to 5.5 hours. At 68°F (20°C), it can take 7 to 9 hours. Higher temperatures also require shaping at lower volume increases (45-50% rise) to prevent overproofing during handling.
Explore Specialized Baking Calculators
Looking for specific dough styles or maintenance schedules? Use our specialized companion utilities: