Food & Cooking⏱ 5 min read
How to Calculate Your Sourdough Starter Feeding Ratio
Sourdough starter health depends on the right flour-to-water-to-starter ratios. Here's how the numbers work, what different hydration levels produce, and how to read your starter's activity.
A sourdough starter is a living culture of wild yeast and bacteria, and its health depends entirely on being fed at the right ratio. Understanding the numbers removes the guesswork and turns sourdough baking from alchemy into science.
The Feeding Ratio Explained
Starter feeding ratios are written as starter : flour : water by weight. A 1:1:1 ratio means equal parts of each.
Ratio 1:1:1:
Keep 50g starter
Feed 50g flour + 50g water
Total: 150g starter (at 100% hydration)
Ratio 1:5:5 (for a long ferment or overnight):
Keep 20g starter
Feed 100g flour + 100g water
Total: 220g starter
Why Higher Ratios Slow Fermentation
A higher ratio (1:5:5) means the yeast has more food to consume before peaking — ideal for overnight fermentation at room temperature. A lower ratio (1:1:1) means it peaks faster — ideal for same-day baking. The ratio effectively controls your baking timeline.
Hydration Levels and Their Effect
HydrationConsistencyBest For
60–70%Thick paste / stiffSlow fermentation, easier to handle
100% (equal flour/water)Thick pancake batterStandard maintenance, most versatile
125%+PourableVery active, faster peak, wetter dough recipes
Hydration % = Water weight ÷ Flour weight × 100
50g flour + 50g water = 100% hydration (standard)
50g flour + 35g water = 70% hydration (stiff starter)
50g flour + 65g water = 130% hydration (liquid starter)
Reading Your Starter's Activity
A healthy starter should roughly double or more in volume within 4–8 hours of feeding at room temperature (20–24°C). Visual signs of peak activity:
- Domed top (not yet starting to fall)
- Visible bubbles throughout
- Strings of gluten visible when you pull a spoon through it
- Smells pleasantly tangy/yeasty — not acetone-sharp (over-fermented) or flat (under-active)
The "float test" (a small piece floats in water) indicates sufficient gas production but is not perfectly reliable — some starters pass but don't actually leaven bread well, and some fail but perform fine.
How Much Starter for a Loaf?
Typical ratio in bread recipe: 15–20% of flour weight
Standard loaf: 450g flour
Starter needed: 450 × 0.15 = 67.5g (use 65–70g)
The starter itself contributes flour and water to the recipe:
At 100% hydration: 70g starter = 35g flour + 35g water
Adjust recipe total flour and water accordingly for accuracy
Maintaining a Smaller Starter (Less Waste)
Most home bakers keep far too much starter.
Minimum viable starter: 20–30g
Feeding 1:5:5 with 20g starter:
+ 100g flour + 100g water = 220g total
Use 180g in recipe, keep 20g for next time.
No waste, always fresh, minimal flour cost.