Baking · starter maintenance
Sourdough starter feeding calculator
Enter how much starter you have and the ratio you want — get exact flour and water weights, your discard amount, and an honest peak-time window.
How the feeding math works
A feeding ratio is written starter : flour : water, always by weight. The first number is your mature starter (the “seed”); the next two are how much fresh flour and water you add relative to it.
flour = seed × flour-parts · water = seed × water-parts
resulting starter = seed + flour + water
So a 1:5:5 feeding of 50 g of starter adds 250 g flour and 250 g water, giving 550 g total. When the flour and water parts are equal, your starter stays at 100% hydration.
Working backwards from a recipe
If your recipe calls for a specific amount of levain, switch to “I need this much levain” mode. The tool divides your target by (1 + flour-parts + water-parts) to tell you how little seed starter you actually need to begin with — so you generate less discard.
Which ratio should you use?
Lower ratios feed the starter less, so it peaks faster and tastes tangier. Higher ratios stretch the time to peak, which is what you want for an overnight build or a cooler kitchen. These windows are at roughly 21–24 °C (70–75 °F):
| Ratio | Peak window | Best for |
|---|
| 1:1:1 | ~3–6 h | Same-day bake; tangier |
| 1:2:2 | ~4–8 h | Daily; evening feed → morning bake |
| 1:3:3 | ~5–8 h | Balanced rise |
| 1:4:4 | ~6–10 h | Overnight boost |
| 1:5:5 | ~8–14 h | Overnight levain; milder |
| 1:10:10 | ~16–24 h | Weekly / before the fridge |
Temperature shifts every one of these — warmer is faster, cooler is slower. That’s why this tool gives a window and a doneness cue rather than a single “ready at 7:42” time the way some calculators do. Your starter doesn’t read clocks.
What does a 1:5:5 feeding ratio mean?
It means one part mature starter to five parts flour and five parts water, by weight. For 50 g of starter that’s 250 g flour and 250 g water. Because the flour and water are equal, the starter stays at 100% hydration.
How do I feed my starter to a specific levain weight?
Switch to “I need this much levain” mode and enter the amount your recipe calls for. The calculator divides that target by (1 + flour parts + water parts) to tell you how much seed starter to begin with, so you make less discard.
How long until my starter peaks?
It depends on the ratio and your kitchen temperature. Lower ratios like 1:1:1 peak in roughly 3–6 hours; higher ratios like 1:5:5 take 8–14 hours at room temperature. Warmer kitchens are faster. Watch for the starter roughly doubling with a domed top rather than relying on the clock.
How much should I discard?
Enter your current starter amount and the calculator shows the difference between what you have and the seed you’re keeping. Reducing how much starter you keep before feeding is the simplest way to cut discard.
Can I use this for a stiff starter?
Yes. Set the water parts lower than the flour parts — for example 1:5:4 — and the calculator reports the resulting starter hydration (80% in that case).