How to read a feeding ratio
A ratio like 1:5:5 means one part existing starter (the "seed"), five parts flour and five parts water, all by weight. Feed 20 g of starter at 1:5:5 and you add 100 g flour and 100 g water. The first number is always the starter you keep back; the other two are the fresh food.
Worked examples. To end up with 150 g at 1:1:1, use 50 g starter, 50 g flour and 50 g water. To feed 20 g of starter at 1:5:5, add 100 g flour and 100 g water for 220 g in total.
A stiff feed of 1:5:2.5 on 20 g of a 100% starter gives a starter of (50 + 10) ÷ (100 + 10) = 54.5% hydration, which is why the calculator shows the hydration you end up with.
Which ratio to use
A bigger ratio gives the yeast and bacteria more food relative to the culture already there, so the starter takes longer to rise and peak. Bakers use that as a dial:
- 1:1:1 for a quick turnaround in a cool kitchen, or a starter that is still getting established.
- 1:2:2 to 1:5:5 for a starter that should be ready in roughly half a day; how long depends heavily on your kitchen's temperature and your flour.
- 1:10:10 or higher to slow things down, for example an overnight feed in a warm room.
Watch your own starter rather than the clock: it is ready when it has risen clearly, has a domed or just-collapsing top and smells pleasantly sour.
The formula
One part = target ÷ (starter + flour + water parts), or seed weight ÷ starter parts
Each ingredient = its parts × one part
Hydration after feeding = (water + water in seed) ÷ (flour + flour in seed) × 100
Limits of this calculator
- It works in weight. Measuring by cups is too inconsistent for starter ratios.
- It cannot predict how long your starter will take to peak; temperature, flour and the culture itself all change that.