Sourdough Starter Calculator
Calculate flour and water feeding ratios for sourdough starter maintenance and recipe use. Enter values for instant results with step-by-step formulas.
Formula
Hydration % = (Water Weight / Flour Weight) x 100
Hydration percentage is water weight divided by flour weight times 100. Feeding ratios like 1:5:5 mean 1 part seed starter to 5 parts flour to 5 parts water by weight. The total weight is divided proportionally among these parts.
Worked Examples
Example 1: Build 200g Starter at 100% Hydration (1:5:5)
Problem: A bread recipe requires 200g of active starter at 100% hydration. You have 50g of existing starter. How much flour and water do you need?
Solution: Feeding ratio: 1:5:5 (total 11 parts)\nSeed starter: 200 x (1/11) = 18g\nFlour: 200 x (5/11) = 91g\nWater: 200 x (5/11) = 91g\nTotal: 18 + 91 + 91 = 200g\nDiscard: 50 - 18 = 32g\nAt 75F, peak in ~7 hours
Result: Seed: 18g | Flour: 91g | Water: 91g | Discard: 32g | Peak: ~7 hours
Example 2: Daily Maintenance Feed (1:3:3)
Problem: You want to maintain 100g of starter at 100% hydration with a 1:3:3 ratio. How much of each ingredient?
Solution: Feeding ratio: 1:3:3 (total 7 parts)\nSeed starter: 100 x (1/7) = 14g\nFlour: 100 x (3/7) = 43g\nWater: 100 x (3/7) = 43g\nTotal: 14 + 43 + 43 = 100g\nDiscard remaining starter before adding fresh feed.
Result: Seed: 14g | Flour: 43g | Water: 43g | Faster peak due to higher starter ratio
Frequently Asked Questions
What does hydration percentage mean for sourdough starter?
Hydration percentage expresses the ratio of water to flour by weight, calculated as water weight divided by flour weight times 100. A 100 percent hydration starter has equal weights of flour and water, making it a thick pancake-batter consistency that is the most common and easiest to maintain. A 50 percent hydration starter has half the water weight compared to flour, creating a stiff dough ball that ferments more slowly and produces more acetic acid for a sharper tang. A 125 percent hydration starter is thinner and more pourable. The hydration of your starter directly affects the hydration calculation of your final dough, which is why knowing it precisely matters for consistent bread.
How often should I feed my sourdough starter?
Feeding frequency depends on where you store your starter and how often you bake. A starter kept at room temperature around 70 to 75 degrees Fahrenheit needs feeding every 12 to 24 hours to stay healthy and active. In warmer environments above 80 degrees, it may need feeding every 8 to 12 hours. If you bake infrequently, store your starter in the refrigerator and feed it once a week. Before using a refrigerated starter for baking, take it out and give it two to three feedings at room temperature over 24 to 48 hours to reactivate it fully. A well-fed starter should roughly double in size within 4 to 8 hours of feeding.
What is sourdough discard and can I use it?
Sourdough discard is the portion of starter removed before each feeding to keep the total volume manageable. Without discarding, the starter would grow exponentially with each feeding and quickly become unwieldy. However, this discard is perfectly usable and should not be wasted. Unfed discard can be used immediately in pancakes, waffles, crackers, pizza dough, flatbreads, muffins, and many other recipes. It adds a mild tanginess and complexity to baked goods. Discard can be stored in the refrigerator for up to a week, and you can accumulate it from multiple feedings. There are entire cookbooks dedicated to creative uses for sourdough discard.
How do I know when my starter is ready to bake with?
A mature, active starter shows several reliable signs of readiness. The most dependable test is the float test: drop a small spoonful of starter into a glass of water, and if it floats, the starter is full of gas and ready to leaven bread. A ready starter should have doubled or tripled in volume since its last feeding, have a domed top, and show lots of bubbles both on the surface and along the sides of the jar. It should smell pleasantly tangy and yeasty, not sharp or like nail polish remover. The ideal time to use starter is at or just past its peak volume, usually 4 to 8 hours after feeding depending on temperature and ratio.
What flour should I use for feeding my sourdough starter?
All-purpose white flour is the most common and reliable choice for maintaining a sourdough starter because it provides consistent results and is widely available. Whole wheat and rye flours contain more nutrients and wild yeast, which makes them excellent for establishing a new starter or giving a sluggish one a boost. Many bakers use a blend of 50 percent all-purpose and 50 percent whole wheat for daily feedings. Bread flour works well due to its higher protein content. Avoid bleached flour as the bleaching chemicals can inhibit fermentation. Consistency matters more than the specific flour type, so once you find what works, stick with it for predictable behavior.
Why does temperature matter for sourdough starter?
Temperature is the single most important environmental factor affecting fermentation speed and flavor development. Yeast activity roughly doubles for every 15 degree Fahrenheit increase in temperature. At 75 to 80 degrees, a starter reaches peak activity in 4 to 6 hours and produces a balanced, mildly tangy flavor. At cooler temperatures around 65 degrees, fermentation slows significantly, taking 10 to 14 hours but producing more complex flavors with higher acetic acid content. Above 85 degrees, the bacteria dominate over yeast, increasing sourness but potentially weakening rising power. Understanding temperature allows you to control your starter like a precision instrument, timing feedings and baking around your schedule.