Feeding ratios, hydration and when a starter is ready
A feeding ratio is written starter : flour : water by weight, so 1:5:5 means one part starter to five parts flour and five parts water. The ratio decides two things at once: how much food the culture gets and how sour it becomes. Feed 1:1:1 and the yeast exhausts the flour quickly, peaking in three or four hours with a mild flavour that suits a same-day bake. Feed 1:10:10 and the same culture takes most of a day to peak and tastes noticeably tangier, because the acetic-acid bacteria have longer to work.
Hydration is simply the water weight divided by the flour weight. A 1:5:5 feed is always 100% hydration regardless of the ratio size, because water and flour are added in equal parts. Change to 1:5:4 and you have an 80% starter — thicker, slower to bubble, and a little easier to handle in hot kitchens. Most recipes assume 100%, so keep that in mind when a formula asks for "100 g of 100% starter".
Time to peak is an estimate, and that is fine
Nothing can predict your starter exactly. A cold kitchen, a young culture, wholemeal flour, chlorinated water and a loose lid all slow it down; a warm spot and a vigorous culture speed it up. The honest way to plan is to estimate, then calibrate: feed 1:5:5 at 24 °C and watch the clock the first time, then set the speed field on this page to match what you saw. As a rule of thumb each additional 8 °C roughly halves the time, which is why the same feed can take four hours in summer and twelve in winter.
How much starter does a recipe need?
Most sourdough formulas express starter as a percentage of the flour weight — the inoculation rate. Bread at 20% inoculation means 500 g of flour needs 100 g of ripe starter; a long, cool ferment might use 10%, while a fast, warm dough might use 30%. Subtract that starter from the formula's flour and water totals, since a 100% starter is half flour and half water: 100 g of starter contributes 50 g of each.
Reference: ratios and what they are for
| Ratio | Peak at 24 °C | Best for |
|---|---|---|
| 1:1:1 | about 3 hours | Reviving a sluggish starter, same-day baking |
| 1:2:2 | about 4 hours | Daily maintenance in a warm kitchen |
| 1:3:3 | about 4½–5 hours | A middle ground that is hard to over-ferment |
| 1:5:5 | about 6 hours | The standard overnight feed |
| 1:10:10 | about 8–9 hours | Fridge storage and less-sour loaves |
Once fed, the starter roughly doubles in volume at peak. After that it collapses, smells sharply acidic and loses the elasticity that lifts a dough, so use it while it is domed rather than waiting for the clock.
Frequently asked questions
What does a 1:5:5 feeding ratio mean?
It is starter : flour : water by weight — one part starter to five parts flour and five parts water. With 20 g of starter you add 100 g of flour and 100 g of water for 220 g total, and the hydration stays at 100% because flour and water are equal.
How often should I feed my sourdough starter?
Daily if it sits at room temperature, or every 5–7 days in the fridge on a 1:5:5 feed. A starter kept warm and fed 1:1:1 needs feeding twice a day at its peak; one stored cold is dormant and only needs refreshing before you bake.
How long until my starter peaks?
At 24°C a 1:1:1 feed peaks in about 3 hours, 1:5:5 in about 6 and 1:10:10 in 8–9; each 8°C cooler roughly doubles that. The tool gives an estimate and a speed field so you can calibrate it to your own culture.
How do I know the starter is ready to use?
It is roughly doubled, domed on top, full of bubbles and pulls back slightly when you tap the jar. A spoonful dropped in water should float. Smell should be pleasantly yeasty and sour, not nail-polish sharp.
Should I discard starter before feeding?
Only if you are keeping the size manageable. Discarding keeps the ratio meaningful and stops the jar overflowing; if you want to keep everything, simply feed a larger ratio such as 1:10:10 with the same amount of starter.
Does starter always have to be 100% hydration?
No. Many bakeries keep a stiffer starter at 50–65% hydration because it ferments more slowly and tastes less sour. If you change hydration, adjust the water in the recipe too: a 60% starter contributes less water per gram than a 100% one.
How much starter do I add to a bread recipe?
Typically 10–30% of the flour weight. 20% is a common middle ground: 500 g of flour takes 100 g of ripe starter, which also supplies 50 g of flour and 50 g of water, so subtract those from the formula.
My starter smells like acetone — is it dead?
No, it is hungry. That smell means the culture has run out of food and is producing alcohol and acids. Feed it at 1:5:5 twice, discarding in between, and it will come back to a yeasty smell and a reliable rise.
A starter and a cold ferment follow the same arithmetic at different temperatures — the reasoning is in How a cold ferment really works.