Sourdough Starter Feeding Ratio Calculator
Pick a ratio, enter how much starter you’re keeping, and get the flour and water to feed it.
Peak estimates assume a healthy starter at roughly 22–24 °C room temperature. Cooler kitchens run slower.
What the ratio means
A feeding ratio is written starter : flour : water, by weight. Feeding at 1:2:2 means that for every gram of starter you keep, you add two grams of flour and two of water — so 20 g of starter gets 40 g of flour and 40 g of water, making 100 g. All the ratios here keep the starter at 100% hydration; only the amount of fresh food changes.
Choosing a ratio
The ratio is really a timer. A small feed like 1:1:1 gives the culture little fresh food, so it peaks fast — typically four to six hours — and turns sour quickly afterwards. Bigger feeds dilute the culture and take longer to peak: 1:2:2 lands around six to eight hours, 1:5:5 around eight to twelve, and 1:10:10 can hold overnight and beyond. Pick the ratio that makes your starter peak when you actually need it, rather than fighting your schedule.
Reading the peak
A ripe starter has domed or just begun to flatten, smells pleasantly tangy rather than harsh, and is full of bubbles through the body of the culture, not just on top. Temperature moves everything: at 26 °C a 1:5:5 feed can behave like a 1:2:2 at 20 °C. If your kitchen runs cold, use a smaller ratio or find a warmer spot; if your starter races past its peak before you wake up, feed it more heavily.
Whatever ratio you settle on, consistency beats cleverness — the same feed at the same times teaches you exactly what “ready” looks like for your jar.
How it works
A ratio of a : b : c is scaled to the starter you are keeping. The flour to add is the kept starter × b ÷ a, and the water is the kept starter × c ÷ a. The total is simply the three added together.
The peak estimate comes from how much fresh flour the culture has to work through, relative to itself — the flour part divided by the starter part. Up to 1× it expects a peak in about 4–6 hours, up to 2× about 6–8, up to 5× about 8–12, and beyond that 12–16. Those windows assume a healthy starter at roughly 22–24 °C.
A worked example
Say you want a ripe starter first thing in the morning and you feed it at ten o’clock the night before. An overnight gap calls for a large feed, so choose 1:5:5 and keep 15 g of starter.
| Flour (15 × 5 ÷ 1) | 75 g |
| Water (15 × 5 ÷ 1) | 75 g |
| Total in the jar (15 + 75 + 75) | 165 g |
| Expected peak (flour is 5× the starter) | 8–12 hours |
A ten o’clock feed should peak somewhere between six and ten the next morning. If your kitchen is cold overnight, expect the later end of that window or beyond; if it is warm, check early.
Frequently asked questions
What is the best sourdough starter feeding ratio?
There is no single best ratio — the right one is whichever peaks when you need it. 1:1:1 peaks fastest, typically in about 4–6 hours at a warm room temperature, while 1:5:5 takes roughly 8–12 and suits an overnight feed. Choose by your schedule, then keep it consistent so you learn what ripe looks like for your jar.
How much flour and water should I feed my starter?
Multiply the starter you keep by each side of the ratio. At 1:1:1, 50 g of starter gets 50 g of flour and 50 g of water. At 1:5:5, 15 g of starter gets 75 g of each. The amount you keep, not the size of your jar, sets the quantities.
What does 1:1:1 mean for a sourdough starter?
Equal weights of starter, flour and water. It is the smallest common feed, so the culture has little fresh food to work through: it rises quickly, peaks within a few hours at a warm room temperature, and turns sour soon afterwards if it is not used.
Why does my starter peak too early or too late?
Temperature is the usual reason. The estimates here assume roughly 22–24 °C; a warmer kitchen speeds everything up and a cooler one slows it down considerably. If your starter peaks before you need it, feed a larger ratio. If it is late, use a smaller ratio or move the jar somewhere warmer.
Do I have to discard starter before feeding?
The ratio is based on how much starter you keep, so discarding is really about keeping feeds small. Keeping 10–20 g and discarding the rest means modest amounts of fresh flour each time. Keep it all, and the flour and water have to grow to match — the jar, and the flour bill, get bigger with every feed.
A free web tool from the makers of The Bake Log — starter feeding reminders, guided bake timelines and a full bake journal. Offline, no account, free to start.
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