Sourdough Starter Feeding Calculator
Feed math for sourdough starter: flour, water, and jar total.
What it does
A sourdough starter is a small culture kept alive by regular feeds. Each feed keeps a spoon of ripe starter and adds fresh flour and water, and the ratio of those parts sets how fast the jar peaks.
The tool above does the feed math. Kept 50 g at 1 to 2 to 2 needs 100 g flour and 100 g water, for 250 g total in the jar. Imperial kitchens get the same answer as 1.8 oz starter with 3.6 oz flour and 3.6 oz water.
Ratio tracks timing. A 1 to 1 to 1 feed peaks in a few hours at warm room temp and suits a morning mix, while 1 to 2 to 2 stretches the peak toward evening. Cold kitchens slow every ratio, warm kitchens speed them.
Jar size follows total weight. A 250 g feed needs headroom above the line for doubling, so a quart jar with a marked band works better than a small cup that overflows at peak.
Discard is a choice, not waste. The spoon kept for the next feed stays small, and the rest leavens pancakes, crackers, or a second loaf when baked through.
How to use
- Pick metric (g) or imperial (oz).
- Weigh kept starter after discard.
- Enter flour ratio, often 2.
- Enter water ratio, often 2.
- Read flour and water to add.
- Read total jar weight to pick jar size.
Formula
- starter
- Kept ripe starter after discard.
- flour ratio
- Flour parts per one starter part.
- water ratio
- Water parts per one starter part.
Ratios read as starter to flour to water by weight. A 1 to 2 to 2 feed triples the jar in a different way than 1 to 1 to 1, so match ratio to kitchen temp and bake timing.
Worked example
Example: 50 g fed 1 to 2 to 2
Metric defaults: 50 g starter fed 1 to 2 to 2. These are also the default values, so the page opens on this answer.
- Kept starter: 50 g.
- Ratio: 1 part starter to 2 flour to 2 water.
- Flour: 50 x 2 = 100 g.
- Water: 50 x 2 = 100 g.
- Total: 50 + 100 + 100 = 250 g.
- Tool shows 100 g, 100 g, 250 g total.
Reference table
| Kept | Ratio | Add each | Total |
|---|---|---|---|
| 25 g | 1 to 2 to 2 | 50 g | 125 g |
| 50 g | 1 to 2 to 2 | 100 g | 250 g |
| 50 g | 1 to 1 to 1 | 50 g | 150 g |
| 1.8 oz | 1 to 2 to 2 | 3.6 oz | 9 oz |
Limits
- Timing guidance only. Culture strength varies by flour and temp.
- Assumes 100 % hydration style feeds. Stiff starters need their own math.
- Does not judge readiness. Peak look and smell still decide.
- Ignores salt. Salt belongs in final dough, not the feed.
Common mistakes
- Feeding cups instead of weights and drifting hydration.
- Keeping a large mother and wasting flour each feed.
- Feeding a cold starter on a warm clock, then missing peak.
- Sealing the jar airtight so pressure builds.
- Adding salt to the feed and slowing the culture.
Try it yourself
Quick checks. Answers sit tucked under each question.
25 g starter at 1 to 2 to 2?
Flour is 25 x 2 = 50 g. Water is 25 x 2 = 50 g. Total is 25 + 50 + 50 = 125 g.
1.8 oz starter at 1 to 1 to 1?
Flour is 1.8 x 1 = 1.8 oz. Water is 1.8 x 1 = 1.8 oz. Total is 1.8 + 1.8 + 1.8 = 5.4 oz, shown as 5 oz total.
Questions
How much flour and water?
Multiply kept starter by each ratio number. Kept 50 g at 1 to 2 to 2 needs 100 g flour and 100 g water, or 250 g total.
Which ratio should I use?
A 1 to 2 to 2 feed suits twice daily baking at room temp. A 1 to 5 to 5 feed stretches to once daily, and 1 to 1 to 1 peaks fastest for a morning mix.
When is the starter ready?
Feed at peak, when domed, bubbly, and just starting to fall. A spoon mark on the jar makes the rise easy to read.
How much starter should I keep?
Keep 25 to 50 g and feed the rest to new dough or discard. Large carries waste flour with no gain in vigor.
Equal cups or equal weights?
Use equal weights of flour and water for a 100 % hydration starter. Volume cups mislead because flour packs, so weigh both.
Is discard safe to eat?
Yes, if raw flour is the risk. Heat the discard portion through in pancakes, crackers, or pizza, and keep the mother culture clean.