Sourdough Starter Feeding Calculator

Enter how much starter you're keeping and your feeding ratio, and get the exact flour and water to add.

Starter to feed (g)

Ratio — starter part

Ratio — flour part

Ratio — water part

Reading a feeding ratio

A ratio like 1:1:1 (starter:flour:water) means equal parts by weight of all three — 50g starter gets fed 50g flour and 50g water. A 1:5:5 ratio feeds much more flour and water relative to the starter kept back, which dilutes it further and slows fermentation, common for a starter that's being fed once a day or less. Flour and water amounts here are always calculated as a multiple of the starter amount you enter.

Why the ratio changes fermentation speed

A tighter ratio like 1:1:1 gives the existing microbial population more food per feeding relative to how much is already there, so it ramps up and peaks faster — useful if you're feeding twice a day or want the starter ready sooner. A looser ratio like 1:5:5 or 1:10:10 stretches that same activity over a longer, slower rise, which suits once-daily feeding or keeping a starter usable over a longer window.

Discard isn't waste, it's just the "keep back" amount

Every feeding, you're only keeping a small amount of the existing starter (the "starter" part of the ratio) and discarding the rest before adding fresh flour and water — that discard is exactly what makes recipes calling for "sourdough discard" possible, and it's fully usable in pancakes, crackers, and other recipes rather than needing to be thrown away.