Sourdough Starter Feeding Calculator
Tell it how much starter your recipe needs and your feeding ratio, and get the exact grams of starter, flour and water to mix, with a little extra left over to keep going.
What the feeding ratio means
A feeding ratio such as 1:2:2 is the proportion, by weight, of ripe starter to fresh flour to water. With 20 g of starter, 1:2:2 means adding 40 g of flour and 40 g of water, for 100 g in total. The first number is how much "old" starter you carry forward, and the other two are the food you give it.
- Low ratios (1:1:1) ferment fast and are ready in a few hours. They're good when you're short on time or reviving a sluggish starter in a warm kitchen.
- Medium ratios (1:2:2 to 1:3:3) are the everyday workhorse. Feed in the morning and it's ready by the afternoon or evening.
- High ratios (1:5:5 to 1:10:10) ferment slowly. Mix one before bed and it peaks in the morning, and it tends to taste milder, because the acids from the old starter are diluted more.
How long until it peaks?
| Ratio | Roughly ready in (about 75 °F / 24 °C) |
|---|---|
| 1 : 1 : 1 | 4–6 hours |
| 1 : 2 : 2 | 6–8 hours |
| 1 : 3 : 3 | 7–9 hours |
| 1 : 5 : 5 | 8–12 hours |
| 1 : 10 : 10 | 12–16 hours |
These are rough starting points. Every starter is different, and temperature matters most: a warm kitchen can cut these times dramatically, and a cool one can double them. Learn your own starter's rhythm.
How to tell it's ready
- It has at least doubled in size and has a domed or just-flattening top.
- It's full of bubbles all the way through, with a light, airy texture.
- It smells pleasantly tangy and yeasty, not sharply of acetone or vinegar. That smell usually means it's past peak and hungry.
- For many bakers, the "float test" (a spoonful floats in water) is a helpful sign, but not a requirement. Whole grain and stiff starters often sink even when perfectly ready.
Tips
- Only build what you need. Instead of feeding a big jar and discarding most of it, use this calculator to mix exactly enough for your recipe plus a little to keep.
- A little whole grain speeds things up. Swapping 10–20% of the flour for whole wheat or rye adds nutrients and makes the starter more active.
- Stiff starters (for example 1:5:2.5, or 50% hydration) ferment more slowly and less sourly. Use the custom ratio to set one up.
- Hydration: your starter's hydration is its water ÷ flour. With equal flour and water it's 100%, which is the assumption most recipes make. The baker's percentage calculator accounts for starter at any hydration.
Frequently asked questions
What's the best feeding ratio for a sourdough starter?
There isn't a single best one. Pick the ratio whose timing fits your schedule: 1:1:1 for a few hours, 1:2:2 for half a day, 1:5:5 or higher to feed at night and bake in the morning.
Does the ratio change my starter's hydration?
Only if the flour and water numbers differ. 1:2:2 and 1:5:5 both keep a 100% hydration starter at 100%. A ratio like 1:5:4 lowers it.
Can I use starter straight from the fridge?
It's best to give it one or two feedings at room temperature first so it's active and predictable. A cold, sluggish starter leads to slow, dense bread.