How to use the starter feeding calculator
- Choose a mode. "I need this much" works backwards from the amount of active starter your recipe needs. "I'm keeping this much" starts from the starter you leave in the jar.
- Pick a feeding ratio, written as starter : flour : water by weight.
- Enter your kitchen temperature and when you'll feed. The calculator estimates when your starter will be at its peak.
Not sure which ratio? Look at the table under the results – it shows when each ratio would be ready, so you can pick the one that fits your day.
Feeding ratios explained
A ratio like 1:2:2 means one part starter, two parts flour and two parts water. The yeast and bacteria in the starter eat through the fresh flour, rise, peak and then fall. More fresh flour per gram of starter means more food, so it takes longer to reach peak.
| Ratio | Peak at ~24 °C / 75 °F | Use it when |
|---|---|---|
| 1:1:1 | 4–6 hours | You want to bake the same day, or your kitchen is cool |
| 1:2:2 | 6–8 hours | An everyday feeding, morning to afternoon |
| 1:5:5 | 9–12 hours | Feed at night, bake in the morning |
| 1:10:10 | 12+ hours | A very warm kitchen, or a long day away |
Temperature shifts all of these. As a rule of thumb, fermentation runs about twice as fast for every 7 °C (roughly 13 °F) warmer, and half as fast for every 7 °C cooler.
How the math works
For example, 100 g at 1:2:2 is 20 g starter, 40 g flour and 40 g water. Feeding the starter you keep? Multiply instead: keep 20 g at 1:5:5 and add 100 g flour and 100 g water.
Tips for a strong starter
- Use it at peak. Mix your dough when the starter has risen and domed, not after it has collapsed.
- Try the float test only as a guide. A spoonful of starter that floats in water is usually ready, but whole-grain starters often sink even when they're strong.
- Add some whole grain. 10–20% whole wheat or rye in each feeding gives the microbes extra nutrients and makes a sluggish starter livelier.
- Keep the discard. Bake it into pancakes or crackers – our discard calculator shows how.
Frequently asked questions
What does a 1:2:2 feeding ratio mean?
One part starter, two parts flour and two parts water by weight. For example, 20 g starter + 40 g flour + 40 g water. The bigger the last two numbers, the more fresh food the yeast get and the longer the starter takes to peak.
Which feeding ratio should I use?
Choose by timing. 1:1:1 peaks in about 4–6 hours at 24 °C / 75 °F, 1:2:2 in about 6–8, and 1:5:5 in about 9–12 – perfect for feeding at night and baking in the morning. In a warm kitchen, use a bigger ratio to slow it down.
How do I know when my starter is at peak?
It has roughly doubled or tripled, the top is domed or just starting to flatten, it's full of bubbles and smells pleasantly sour-yeasty. Mark the jar with a rubber band after feeding so you can see the rise.
Do I have to discard starter before feeding?
Keeping only a small amount before feeding keeps flour costs down and keeps the ratio meaningful. You can bake with the discard instead of throwing it away – see our discard calculator.
Can I change my starter's hydration?
Yes. Feed with less water than flour for a stiff starter (for example 1:2:1 = 50% hydration), which ferments more slowly and tastes less sour. Enter any custom ratio above and the calculator shows the resulting hydration.