Sourdough starter calculator

What a starter actually is

A sourdough starter is a stable symbiotic culture of wild yeast and lactic acid bacteria (primarily Lactobacillus and Saccharomyces species). The yeast produces CO2 (rise) and ethanol; the bacteria produce lactic and acetic acid (tang). In a healthy starter, these populations stabilize in a ratio that depends on your feeding schedule, flour, and temperature.

Your starter has a microbiological fingerprint unique to your kitchen. A San Francisco starter shipped to New Zealand rapidly becomes a New Zealand starter within weeks, because local yeasts and bacteria colonize. The mythology of "100-year-old starters from grandma" is mostly that — the original microbes are long replaced.

The 1:1:1 feeding ratio

The beginner standard is 1:1:1 by weight — equal parts starter, flour, water. Example: 25g starter + 25g flour + 25g water = 75g new starter. At 75°F, peaks in 4-6 hours, then falls. This ratio works, keeps the starter active, and is easy to track.

For slower fermentation (maintain in fridge, feed every week): use 1:5:5 or 1:10:10. Less starter, more food, takes 12-18 hours to peak. Better for keeping a starter alive during travel.

For faster activation (morning refresh before a bake): 1:2:2 or 1:3:3 at warm (78°F) temperature. Peaks in 3-4 hours.

How to feed: the full protocol

1. Weigh an empty jar. Record tare.
2. Keep only a small amount of starter (25g is plenty). Discard the rest, or use "discard" in pancakes, crackers, or pizza dough.
3. Add equal weights of flour and water. For 25g starter: 25g flour + 25g water. Stir until combined. Small bubbles should appear within 30 minutes.
4. Mark the jar level with a rubber band. This tracks when the starter peaks.
5. Wait 4-12 hours depending on temperature and ratio. Starter should roughly double.
6. Repeat daily at room temp, or 1-2x weekly if stored in fridge.

The float test (and why it's not always accurate)

Drop a teaspoon of starter into water. If it floats, the starter is "ready" (gas-filled and active). This test works for 1:1:1 starters at peak. It fails for very wet starters (100%+ hydration naturally float regardless of activity) and very dry starters (sink even at peak). Better indicators: volume increase (doubled is the target), smell (pleasant fermented, not acetone or vinegar harsh), and domed top.

Troubleshooting common starter problems

• Liquid on top (hooch): Starter is hungry. Gray/clear hooch is normal. Black or pink hooch means discard and restart. Feed 2x daily for 3 days to recover.
• Stopped rising: Usually temperature. Move to warmer spot (78°F). Also: flour quality — switch to freshly milled whole wheat for 2 feedings to reinvigorate.
• Smells like acetone/nail polish: Under-fed. Feed 1:5:5 twice daily for 2 days.
• Smells like vomit/harsh cheese: Bacterial imbalance. Feed twice daily, switch to bread flour if using AP.
• Mold (pink, orange, fuzzy): Discard and start over. Mold on the surface is contamination, not fermentation.
• Starter rises but deflates immediately: Peaked and fell — you missed the window. Still fine to bake with, but timing is off. Feed again.

Maintaining a starter with minimal effort

You don't need to feed daily. For weekly bakers: feed the starter, let it peak at room temperature (4-6 hours), then fridge it. Pull out the night before you plan to bake, feed at 1:1:1, let it peak at room temp, use. Return remaining to fridge after re-feeding. This protocol keeps the starter alive with one 5-minute feeding per week.

For travel: dry the starter. Spread a thin layer on parchment, dry at 150°F oven (or warm dehydrator, or sunny windowsill) until brittle. Crumble into a sealed jar. Lasts 1+ years. Rehydrate by soaking 1 tbsp dried flakes in 1 tbsp water until paste forms, then feed 1:1:1 daily for 3-5 days until active.

Starting a starter from scratch (7-14 days)

1. Day 1: 50g whole wheat flour + 50g water (filtered or dechlorinated). Stir, cover loosely, room temp.
2. Day 2: Some bubbles should appear. Feed: 50g flour + 50g water. Total: 200g.
3. Day 3-5: Starter may rise and fall. Discard half (100g), feed remainder 50g flour + 50g water. Switch to AP or bread flour on Day 3.
4. Day 5-7: Should be doubling in 6-8 hours. If not, continue daily feeds, consider warming.
5. Day 7-14: Stable starter. Doubles in 4-6 hours at 1:1:1. Passes float test. Ready to bake.

Flour choice makes or breaks the starter

Whole wheat or rye flour has more wild yeasts and bacteria on the grain surface. Starting with 100% whole wheat for the first 3 days, then transitioning to AP or bread flour, gives the fastest and most reliable start. Chlorinated tap water kills microbes — use filtered water or leave tap water uncovered overnight to let chlorine evaporate.

Using starter in bread

A healthy starter is used at its peak (2-4 hours after feeding, when doubled). For a basic loaf: 100g starter + 500g flour + 350g water (70% hydration) + 10g salt. The starter contributes both leavening and flavor. Bulk ferment 4-6 hours, shape, cold retard overnight, bake next morning. Longer cold retard (24-48 hours) increases flavor and extends shelf life.

Related: dough hydration, pizza dough math, cups to grams, recipe scaler.

Why your starter will outlive you

A well-maintained starter is effectively immortal. As long as you feed it occasionally, the microbes reproduce indefinitely. Many starters get passed down through generations or shared among baking communities. The oldest documented continuously-maintained starter is claimed to be 160+ years old (Boudin Bakery's original, San Francisco). Yours won't be, but it'll outlive many appliances in your kitchen. Treat it with respect.

Worked example: a weekly bake from a fridge starter

Protocol for someone who bakes one loaf per week from cold storage:

1. Thursday 8 PM: Pull starter from fridge. Discard down to 25g. Feed 25g flour + 25g water. Leave on counter overnight.
2. Friday 8 AM: Starter should be domed and bubbly (6-8 hrs at 70°F). Use 100g for levain: 25g starter + 50g flour + 50g water. Return remaining starter to fridge.
3. Friday 2 PM: Levain peaks. Mix dough: 500g flour + 375g water (75% hydration) + 100g levain + 10g salt. Bulk ferment 4-5 hrs with 4 stretch-and-folds.
4. Friday 7 PM: Shape, place in floured banneton, fridge overnight.
5. Saturday 8 AM: Bake in preheated Dutch oven at 500°F with lid for 20 min, 450°F without lid for 20-25 min. Cool 1 hour before cutting.

Total hands-on time: 45 min across two days. Fridge-held starter, active one weekend.

Worked example: reviving a neglected starter

Forgotten for 3 weeks in the fridge. Greenish hooch on top, smells like acetone. Recovery:

1. Pour off hooch. Discard all but 1 tsp of starter.
2. Feed 1:5:5 with whole wheat flour (5g starter + 25g whole wheat + 25g water). Whole wheat wakes the microbes faster than white.
3. Leave 12 hrs at 75°F. Some bubbling.
4. Second feeding: 10g from previous + 50g white flour + 50g water. 8-12 hrs.
5. Third feeding: same ratio. After 6-8 hrs should pass float test.
6. Fourth feeding: standard 1:1:1. If it doubles in 4-6 hours, ready to bake.

Total recovery time: 2-3 days. Starters are remarkably resilient.

Starter diagnostics: reading your jar

• Rises fast and flat (few bubbles): too warm or too little food. Move to cooler spot or increase feed ratio.
• Rises slow with big bubbles: normal for low-yeast high-bacteria starter. Reduce bacterial activity by feeding more frequently.
• Doesn't rise but smells pleasant: yeast is dormant. Add 10% whole wheat to next feeding, warm to 78°F.
• Rises and falls within 2 hours: very active. Either bake now or slow it with a larger feed ratio (1:5:5).
• Domed top that stays put: at peak, ideal for levain prep.
• Flat top with crust: past peak; feed again or fridge.

Flour choice deep dive

• Starting a new starter: 50/50 whole wheat + rye for first 3 days. Highest microbe population on the bran.
• Maintenance starter: bread flour (King Arthur) for consistency. Or 20% whole wheat / 80% bread flour for flavor depth.
• High-ratio rye starter: unique tang, slightly sourer. Requires warmer environment (78°F+) for consistent activity.
• Organic unbleached flour: better microbial food than bleached. Bleaching kills some of the beneficial molds on the grain.
• Freshly milled flour (home grain mill, Mockmill): dramatically more active. Some bakers keep a 100% fresh-milled starter for bread.

Water quality

Chlorinated tap water kills microbes slowly. Options:

• Leave tap water uncovered overnight — chlorine evaporates.
• Boil and cool — removes chloramine (harder to evaporate than chlorine).
• Filter (Brita, refrigerator filter) — reduces both chlorine and chloramine.
• Distilled water — works but lacks trace minerals starter uses. Mix 50% distilled / 50% tap if tap has weird mineral profile.

Temperature control tactics

• Ideal starter temp: 75-78°F for active maintenance.
• Cold home (65°F): put starter in oven with light on (creates ~76°F). Or use a proofing mat ($30).
• Hot kitchen (82°F+): starter ferments fast; reduce feed to once daily or keep in fridge.
• For slow overnight rises: fridge (38°F) effectively pauses activity.
• Activating cold starter: allow 2 hours on counter before first feed.

Using the discard productively

Starter discard has plenty of flavor uses. Standard 100g discard recipes:

• Discard crackers: 100g discard + 100g flour + 30g olive oil + 5g salt + herbs. Roll thin, bake 350°F for 15 min.
• Discard pancakes: 100g discard + 1 egg + 50g flour + 1 tsp baking powder + pinch salt + 30g milk.
• Discard pizza dough: 100g discard + 200g flour + 100g water + 5g salt + 5g olive oil. Rest 4 hrs room temp. Stretches like regular dough.
• Discard waffles: 100g discard + 1 egg + 30g melted butter + 30g milk + 40g flour. Crisp edges from the discard's acidity.

FAQ

How old does a starter need to be before it bakes good bread? 2 weeks is the typical benchmark. Before that, the yeast/bacteria ratio is unstable and bread may be dense or sour-off.

Why did my starter suddenly stop rising after months of success? Usually temperature shift (kitchen moved colder), flour change (bought store-brand instead of King Arthur), or contamination (new jar, unwashed). Try 2-3 aggressive feedings with warm environment.

Can I freeze starter? Yes. Feed, let peak, portion into 50g balls, freeze in bag. Revives within 2-3 feedings of thawing.

Why is my starter so sour? Too much bacteria relative to yeast. Fix: feed more frequently (every 6-8 hrs instead of 24), and at higher ratio (1:5:5). This promotes yeast over bacteria.

What's the ideal starter hydration? 100% (equal flour and water by weight) is the beginner standard. Some bakers maintain stiff 50% starters (more sourness, more yeast activity) for specific European loaves.

Can I bake with starter straight from the fridge? Not ideal. Cold starter won't rise well. Feed and let peak at room temp first.

Why does my starter smell like glue or nail polish remover? Acetone smell = underfed, high bacterial stress. Feed twice in one day, and the smell resolves in 12-24 hrs.

Do I need to change jars? Clean jar once a week if maintaining. Old crusty residue harbors wild molds. Transfer fresh starter to clean jar during feeds.

Can I skip feedings when traveling? Fridge-stored starter tolerates 2-3 weeks without feeding. Longer than 3 weeks, expect a slow recovery but not death. A month+ may need the revival protocol above.