starter : flour : water, by weight. That's all it is.
A 1:1:1 feed means equal parts of each — 50 g of old starter, 50 g of flour, 50 g of water. A 1:5:5 means 20 g of old starter against 100 g of flour and 100 g of water. The first number is how much culture you carry forward; the other two are how much food you give it.
So the ratio is really a dilution. A bigger ratio means fewer microbes spread across more food, which means they take longer to eat through it. That's the whole mechanism:
| Ratio | Peak at ~75°F | Use when |
|---|---|---|
| 1:1:1 | 4–6 hours | Baking today; reviving; warm kitchen |
| 1:2:2 | 6–8 hours | The everyday default |
| 1:5:5 | 10–12 hours | Feed at night, use in the morning |
| 1:10:10 | 16–24 hours | Once-a-day feeding, or a hot kitchen |
These are approximations at around 75°F / 24°C with white flour. Your kitchen will shift them, and that's the point of the next section.
Ratio is the lever people reach for. Temperature is the lever that's actually stronger.
Fermentation roughly doubles in speed for every 17°F / 9°C. A starter that peaks in 8 hours at 70°F will peak in about 4 at 80°F. That's a bigger swing than moving from 1:2:2 to 1:5:5 gets you, and it's why the same feeding schedule behaves completely differently in January and July.
The practical version: change one at a time. If your starter is peaking too early and collapsing before you're ready, either feed it a bigger ratio or move it somewhere cooler — not both, or you'll have no idea which worked.
A small ratio fed frequently — 1:1:1 twice a day — keeps the culture in constant abundance. Yeast dominates, acid stays low, and the bread comes out mild and slightly sweet.
A large ratio, or a small one left too long, lets the culture run to exhaustion between feeds. Acid accumulates, and the balance shifts toward the acetic end — sharper, more vinegary. Neither is wrong; they're different breads.
If you want a milder loaf, feed more often at a smaller ratio and use the starter at peak. If you want more sour, stretch the interval and let it sit a little past peak. That's a more reliable dial than anything you do to the dough later.
Most people maintain far too much starter, then feel guilty about the discard. The fix is arithmetic: work out how much you actually need, then keep just over it.
The Calibration Loaf takes 100 g. Keep 20 g in the jar between bakes and feed it 1:2:2 the night before — that's 20 g of starter, 40 g of flour, 40 g of water, giving you exactly 100 g and nothing wasted. If you're not baking, maintain 10–20 g and your discard drops to almost nothing.
The jar of accumulating discard in your fridge isn't a law of sourdough. It's a symptom of keeping 300 g of starter when you needed 20.
Notes from the counter
Feeding ratios are where sourdough advice gets weirdly dogmatic. People will tell you 1:1:1 is wrong, or that you must do 1:5:5, as though there's a correct answer independent of your kitchen and your schedule.
There isn't. The ratio is a way of asking "how long until this thing is ready?" and the only right answer is the one that lands the peak at a time you're actually going to be home.
Pick the ratio that makes the timing convenient and hold it constant for two weeks. A starter fed predictably becomes predictable, which is the only property you actually need from it.