Most starter instructions say something like "feed it equal parts flour and water". That works, but it hides the two things that actually matter: the ratio of old starter to fresh food, which sets how fast the starter peaks, and the total amount you build, which should match what your recipe needs. Get both right and you stop throwing away jars of discard and stop waiting around for a starter that peaked while you slept.
What a feeding ratio means
A ratio such as 1 : 5 : 5 is starter : flour : water by weight. Take 10 g of ripe starter, add 50 g of flour and 50 g of water, and you have 110 g of fed starter at 100% hydration (equal flour and water). The first number is always the seed — the old starter you carry over — and the other two are fresh food. Because the flour and water are equal, the starter's hydration stays at 100% no matter which ratio you use.
The bigger the food multiple, the more each yeast cell and bacterium has to eat, and the longer the population takes to grow, use up the food and peak. That is why ratio is your main timing control, far more than the absolute amount: 20 g and 200 g of starter fed at 1 : 5 : 5 peak at about the same time.
Step 1: decide how much starter you need
Start from the recipe. A loaf with 500 g of flour and 20% levain needs 100 g of ripe starter. Add a buffer for what clings to the jar and spatula — 10–20 g is plenty — and, if you keep a starter going, the 10–20 g you will carry over to the next feed. So the target for this bake is about 100 + 10 + 10 = 120 g.
Then divide by the sum of the ratio. At 1 : 5 : 5 the parts add up to 11, so each part is 120 ÷ 11 ≈ 10.9 g:
| Ratio | Parts | Starter | Flour | Water |
|---|---|---|---|---|
| 1 : 1 : 1 | 3 | 40 g | 40 g | 40 g |
| 1 : 2 : 2 | 5 | 24 g | 48 g | 48 g |
| 1 : 5 : 5 | 11 | 11 g | 55 g | 55 g |
| 1 : 10 : 10 | 21 | 6 g | 57 g | 57 g |
All four rows make 120 g. What differs is how long they take to be ready.
Step 2: pick the ratio that fits your schedule
For a mature, active starter at a typical room temperature of about 72°F (22°C), common experience — reported by many bakers testing their own starters — looks roughly like this: 1 : 1 : 1 peaks in about 3–5 hours, 1 : 2 : 2 in about 5–8 hours, 1 : 5 : 5 in about 8–12 hours and 1 : 10 : 10 in about 12–16 hours. Temperature moves all of these a lot. As a rule of thumb, every 8°C (about 14°F) cooler roughly doubles the time and every 8°C warmer roughly halves it.
| Room temperature | 1 : 1 : 1 | 1 : 2 : 2 | 1 : 5 : 5 | 1 : 10 : 10 |
|---|---|---|---|---|
| 64°F (18°C) | ≈ 6 h | ≈ 9 h | ≈ 13 h | ≈ 17 h |
| 72°F (22°C) | ≈ 4 h | ≈ 6½ h | ≈ 9½ h | ≈ 12 h |
| 79°F (26°C) | ≈ 3 h | ≈ 4½ h | ≈ 7 h | ≈ 8½ h |
These are estimates for planning, not promises. Read them as "which ratio gets me close to my schedule", then adjust after one or two feeds. A practical pattern for an evening bake: feed 1 : 2 : 2 in the morning. For a morning bake: feed 1 : 5 : 5 or 1 : 10 : 10 before bed so it peaks around breakfast instead of at 3 a.m. Many bakers use smaller ratios in winter and larger ones in summer for exactly this reason.
How to tell it is ready
The clock only tells you when to look. A starter at peak has roughly doubled or tripled, has a domed top with bubbles throughout, smells pleasantly sour and yeasty, and a spoonful holds together and looks airy. Just after peak the dome flattens and streaks appear on the jar walls — still fine for most breads. Long past peak it collapses, turns runny and smells of acetone or vinegar; it will still raise bread, but slowly and sourly. Put a rubber band at the starting level so you can see the rise.
Keeping a small starter
You do not need hundreds of grams in the jar. Between bakes, keep 20–50 g. A small maintenance feed such as 5 g starter + 25 g flour + 25 g water (1 : 5 : 5) wastes almost nothing. When you plan to bake, do one build from that small amount straight to the target weight for your recipe, as in step 1. If the build needs more starter than you have, do two feeds in a row: for example 10 g at 1 : 2 : 2 makes 50 g, which can then be fed at 1 : 1 : 1 to 150 g.
In the fridge, starters slow to a crawl. A common routine is a feed at 1 : 5 : 5 or stiffer, an hour or two at room temperature, then refrigeration for up to a week or two. Before baking, give it one or two room-temperature feeds to wake it up.
Flour, hydration and other variables
- Whole grain and rye flour carries more nutrients and wild microbes than white flour, so a starter fed with it usually peaks faster at the same ratio. Many bakers use 10–20% whole wheat or rye in the feed for a livelier starter.
- Stiff starters (50–60% hydration, for example 1 : 5 : 2.5) ferment more slowly and taste less sour, which is handy for long gaps. Changing the starter's hydration also changes your dough's true hydration slightly; the sourdough hydration calculator handles any starter hydration.
- Young starters — under a few weeks old — do not follow these timings yet. Keep them at 1 : 1 : 1 or 1 : 2 : 2 in a warm spot until they double reliably within 4–8 hours.
- Water temperature sets the starting temperature of the feed. Lukewarm water (about 80°F, 27°C) gives a slow kitchen a head start; cool water slows a hot one.
Worked example
You want to bake two 900 g sourdough loaves tomorrow at 9 a.m. The sourdough formula calls for 20% levain on about 1,017 g total flour, so about 203 g of levain. Add 15 g for the jar and 15 g to keep: about 235 g. Your kitchen is 68°F (20°C) at night, and you feed at 10 p.m., 11 hours before you mix. At 20°C the estimates are about 11 hours for 1 : 5 : 5, so 1 : 5 : 5 fits: 235 ÷ 11 = 21.4 g per part → 21 g starter, 107 g flour, 107 g water. In the morning, scoop out 203 g for the dough and keep the rest as tomorrow's seed.
The starter feeding calculator does this arithmetic for any target, ratio and temperature, and the sourdough hydration guide explains how the levain you build is counted in your dough.