Why the feeding ratio changes how often you need to feed
The ratio describes how much new food (flour and water) you're giving the starter relative to how much starter culture you're keeping. A 1:1:1 ratio adds an equal amount of fresh flour and water to the existing starter — this dilutes the culture less, so it consumes its food faster and needs feeding again sooner (often within 12 hours at room temperature). A 1:5:5 or 1:10:10 ratio dilutes the starter much more with fresh food, giving it more to work through before it's exhausted — useful for people who don't want to feed daily, or who keep their starter in the fridge and feed less often.
Choosing a ratio for your baking schedule
If you bake often and keep your starter at room temperature, 1:1:1 or 1:2:2 keeps it vigorous and ready to use most days. If you bake occasionally and keep your starter refrigerated between bakes, a larger ratio (1:5:5 or higher) lets you feed less frequently without the starter starving between feedings — though it'll typically need a warm-up feeding or two at a smaller ratio before baking, to bring it back to peak activity.
FAQ
Does the flour-to-water ratio within a feeding have to be 1:1? Most standard feeding schedules use equal flour and water (100% hydration) for simplicity and consistency, though some bakers vary this deliberately for specific dough hydration goals.
What happens if I don't discard any starter before feeding? The starter volume grows with every feeding if you don't discard some first — over time this becomes an impractically large amount unless you're baking large batches regularly, which is why most routines include discarding most of the starter before each feed.