Starter Feeding Calculator

Why feeding your starter matters

A sourdough starter is a living colony of wild yeast and lactic acid bacteria. Every time you feed it, you give those organisms fresh flour to consume. The sugars and starches in flour fuel fermentation — yeast produces carbon dioxide (the gas that makes bread rise) and bacteria produce the acids that give sourdough its flavor. Without regular feeding, the colony runs out of food, acid builds up, and the yeast goes dormant.

Feeding is not just maintenance. It is how you control the character of your bread. The ratio of old starter to fresh flour and water, combined with the temperature of your kitchen, determines how fast your starter peaks, how sour it tastes, and how much leavening power it delivers to your dough.

How ratios work

A feeding ratio is written as starter : flour : water by weight. A 1:1:1 ratio means equal parts of each — keep 50g of starter, add 50g of flour and 50g of water. A 1:5:5 ratio means five times as much flour and water as starter — 50g of starter gets 250g of flour and 250g of water. The ratio controls two things: how much food is available per organism, and how diluted the carried-over acid is after feeding.

Low ratios (1:1:1) give organisms a smaller food supply relative to their population. The starter peaks faster — typically 4 to 8 hours at room temperature — because there are already enough yeast and bacteria to consume the flour quickly. The tradeoff is that acidity from the previous cycle carries over, which can make the final bread more sour. This is the standard maintenance ratio for daily feeding.

Higher ratios (1:3:3 to 1:5:5) dilute the existing population and give it far more food to work through. Peak time stretches to 8–16 hours depending on temperature. The extra time allows yeast to build a larger population before peaking, which gives you stronger leavening power. The dilution also reduces carried-over acidity, so the resulting bread tends to be milder and more complex in flavor rather than sharply sour. Use higher ratios when baking artisan loaves where you want nuance, or when you need to time your bake around a long overnight schedule.

Custom ratios let you fine-tune further. You can use a higher water ratio than flour ratio to make a more liquid starter (say 1:2:3), which favors bacterial activity. Or feed with less water for a stiffer starter (1:3:2) that ferments more slowly and lasts longer between feeds. Stiff starters are common in Italian baking traditions like panettone, where a slow, controlled fermentation is essential.

Temperature and timing

Temperature is the single biggest lever you have over fermentation speed. Yeast and bacteria are more active in warmth and slow down in cold. The relationship is roughly linear across the range most home bakers work within.

At 80°F (27°C), fermentation is aggressive. A 1:1:1 feed can peak in as little as 4 hours. This is useful when you need your starter ready fast, but the window between peak and overfermentation is narrow. Watch it closely.

At 72°F (22°C) — typical room temperature — expect about 6 hours to peak with a 1:1:1 ratio. This is the most forgiving temperature for scheduling. You can feed in the morning and use the starter by mid-afternoon, or feed before bed and bake first thing.

At 65°F (18°C), the pace slows noticeably. A 1:1:1 feed takes around 10 hours. This is useful in warm climates where you want to slow things down without refrigerating. It is also the range where you will notice more complex flavors developing, as the longer fermentation gives bacteria time to produce a wider range of organic acids.

Below 65°F, fermentation becomes increasingly sluggish. At 55°F it may take 18–24 hours to peak. The fridge (38–40°F) puts the starter into near-dormancy — useful for weekly feeding schedules but not for baking day. If you refrigerate your starter, plan to take it out and give it at least one room-temperature feed before using it in dough.

Above 80°F, things move fast. At 85–90°F a 1:1:1 feed can peak in 2–3 hours. Some bakers use a proofing box at these temperatures intentionally, but you need to monitor closely. The risk is that the starter overferments and collapses before you catch it, which means weaker leavening and excessive acidity. Once your starter is at peak, use our hydration calculator to dial in your dough’s water ratio.

Signs your starter is ready

Volume. A healthy starter should roughly double in size from its post-feeding level. Some vigorous starters triple. Mark the container with a rubber band or tape after feeding so you can track the rise.

Dome. At peak, the surface should be slightly domed or flat. If it is sunken or concave, it has already passed peak and started to collapse. You can still use it, but leavening power is reduced.

Bubbles. You should see bubbles throughout the starter, not just on top. A cross-section (use a clear container) shows an airy, sponge-like texture from top to bottom. Surface bubbles alone can be misleading.

Float test. Drop a small spoonful into room-temperature water. If it floats, there is enough trapped gas to leaven bread. This test is not perfect — very high-hydration starters sometimes float even when underdeveloped — but combined with the other signs it is a reliable confirmation.

Troubleshooting a sluggish starter

If your starter takes far longer than expected to peak or barely rises at all, work through these possibilities in order.

Check your flour. Whole grain flours (whole wheat, rye) provide more nutrients and wild yeast than white flour. If you have been feeding with all-purpose, try switching to a 50/50 blend of all-purpose and whole wheat for a few feeds. The extra minerals and enzymes can kick-start activity.

Check your water. Heavily chlorinated tap water can suppress microbial activity. If your municipal supply is high in chloramine (many cities switched from chlorine), try filtered water or let tap water sit uncovered for 24 hours. Chlorine evaporates; chloramine does not, so a basic carbon filter handles it.

Check your temperature. If your kitchen runs cool (below 68°F), your starter is simply working slowly. Move it to a warmer spot — on top of the fridge, near (not on) a radiator, or inside an oven with just the light on. Even a few degrees makes a noticeable difference.

Check your schedule. If you have been feeding once a day with a 1:1:1 ratio but your kitchen is warm, the starter may be exhausting its food supply and collapsing between feeds. Either feed twice daily or switch to a higher ratio (1:2:2 or 1:3:3) so it has enough food to stay active between feedings.

Be patient. A brand-new starter can take 7 to 14 days to develop a stable, vigorous culture. During the first week you may see a burst of activity around day 2–3 followed by a quiet period. This is normal — leuconostoc bacteria cause the early burst, but they die off as acidity rises and are replaced by the lactobacillus strains that sustain long-term fermentation. Keep feeding on schedule and it will come around.