How to Make Sourdough Starter from Scratch

By Warm Oven Bakes Editorial Team · Updated 2 November 2026

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Every loaf of sourdough begins with a starter: a jar of flour and water that's alive with wild yeast and bacteria. Learning how to make sourdough starter from scratch takes no special ingredients, just flour, water, a jar and about one to two weeks of daily feeding.

This guide gives you a day-by-day schedule, explains what's normal along the way (including the "false rise" that fools many beginners), and shows how to tell when your starter is ready to bake with. It follows the widely used flour-and-water method; every kitchen is different, so watch your starter rather than the calendar.

What is a sourdough starter?

A sourdough starter is a fermented mixture of flour and water that contains a community of wild yeasts and lactic acid bacteria. The yeasts produce carbon dioxide, which makes bread rise, and the bacteria produce acids, which give sourdough its tangy flavor and help it keep.

These microbes are already present on flour and in your kitchen environment. By mixing flour and water and feeding the mixture regularly, you create conditions where the right yeasts and bacteria thrive and others fade away. Once established, a starter can be kept going indefinitely with regular feedings.

You may also hear a starter called a levain (often meaning a portion of starter built up for a specific bake) or a mother.

What you need

Flour (whole wheat/rye kick-start)

Whole-grain flours, such as whole wheat or rye, contain more of the nutrients and naturally present microbes that help a starter get going, so many bakers use them for the first few days. After that you can switch to unbleached all-purpose or bread flour, or keep feeding a mix. Avoid bleached flour, which can be slower to ferment.

• Days 1 to 3: whole wheat or rye flour (or half whole-grain, half all-purpose)
• Day 4 onward: unbleached all-purpose or bread flour, or a mix with some whole-grain

Water

Use lukewarm water, around 75 to 80°F (24 to 27°C). If your tap water is heavily chlorinated, let it sit out uncovered for a few hours, or use filtered water. Many bakers use tap water successfully, so start with what you have and switch only if your starter seems sluggish.

Jar and scale

• A clear glass jar of about 1 quart (1 liter), so you can see the bubbles and rise. A wide mouth makes stirring easier.
• A loose lid, a cloth or plastic wrap with a few holes. Starters release gas, so don't seal them tightly.
• A kitchen scale, since starters are fed by weight. Measuring by cups is much less accurate.
• A rubber band or tape to mark the level after each feeding, so you can see how much it rises.
• A spatula or spoon for stirring.

Shop sourdough starter jars on Amazon

Shop digital kitchen scales on Amazon

How to make sourdough starter: day-by-day schedule

Keep your starter somewhere consistently warm, ideally around 70 to 78°F (21 to 26°C). Cooler kitchens slow everything down; that's fine, it just takes longer.

Day 1

1. In your jar, mix 50 g whole wheat or rye flour with 50 g lukewarm water until no dry flour remains. It will look like a thick paste.
2. Scrape down the sides, cover loosely and mark the level with a rubber band.
3. Leave at room temperature for 24 hours.

Days 2-3: the false rise

Day 2: you may see a few bubbles, or nothing at all. Both are normal. Stir, cover and leave for another 24 hours. (Some methods feed on day 2; skipping a feed this early gives the culture time to wake up.)

Day 3: you might see a big burst of activity: lots of bubbles, a noticeable rise and a strong smell. This is often called the false rise. Early activity is commonly driven by bacteria that thrive at first and then decline as the starter becomes more acidic. It's exciting, but the starter isn't ready yet.

Now start feeding:

1. Discard all but 50 g of the starter.
2. Add 50 g flour and 50 g lukewarm water. Mix well, scrape down, mark the level and cover loosely.

Days 4-7

Around day 4 or 5, many starters go quiet after the false rise. Don't give up; this is normal. The yeasts and bacteria you want are slowly taking over.

Each day (once or twice a day):

1. Discard all but 50 g of starter.
2. Feed with 50 g flour and 50 g lukewarm water.
3. Stir well, mark the level and cover loosely.

From day 4 you can switch to all-purpose or bread flour, or keep part whole-grain. Feeding twice a day, about 12 hours apart, often speeds things up once you see steady activity again.

You'll start to notice:

• More regular bubbles throughout the starter
• A rise after each feeding, getting more predictable
• A smell that shifts from sharp or unpleasant to pleasantly sour, yeasty or like yogurt

Days 7-14: when it's ready

Keep feeding once or twice a day. A starter is typically ready somewhere between 7 and 14 days, though cool kitchens can take longer. It's ready when it reliably doubles in volume within about 4 to 8 hours of feeding, for several days in a row, and looks bubbly and domed at its peak.

How to tell your starter is ready (float test and doubling)

Doubling (the most reliable sign): after a feeding, your starter should at least double in volume within about 4 to 8 hours at warm room temperature, with bubbles throughout and a slightly domed top at its peak. When it does this consistently for two or three days, it's ready.

The float test: drop a spoonful of starter into a glass of water. If it floats, it's full of gas and probably active enough to bake with. It's a handy check, but not foolproof: a well-established starter that's past its peak, or a very wet starter, can sink and still bake good bread. Use it alongside the doubling test, not instead of it.

Other signs:

• A pleasant, tangy aroma (not acetone-like or rotten)
• A web of bubbles when you pull a spoon through it
• A texture like thick batter that's light and stretchy at its peak

Feeding ratios and maintenance

The schedule above uses a 1:1:1 ratio: equal weights of starter, flour and water (for example, 50 g starter + 50 g flour + 50 g water). This is also called a 100% hydration starter, because the water weighs the same as the flour.

Other common ratios:

The more flour and water you add relative to starter, the longer it takes to reach its peak.

Counter vs fridge

• On the counter: feed once or twice a day. Best if you bake often.
• In the fridge: feed it, let it sit at room temperature for an hour or two, then refrigerate. Many bakers feed a refrigerated starter about once a week. Before baking, take it out and give it one or two room-temperature feedings until it's doubling reliably again.

What to do with discard

The starter you remove before each feeding is called discard. You don't have to throw it away:

• Keep it covered in the fridge and use it within about a week; discard it if you see mold.
• Add it to pancake, waffle, cracker or flatbread recipes designed for sourdough discard.
• Fold some into pizza dough for flavor; see our homemade pizza dough.
• Once your starter is established, keep less starter (for example, 20 to 25 g) to reduce discard.

Can you make sourdough starter with yeast?

You can add a pinch of commercial yeast to flour and water to make a quick, bubbly mixture, but it won't be a true sourdough starter. Commercial yeast is a single strain that dominates the mixture, and you won't get the same mix of wild yeasts and lactic acid bacteria that give sourdough its flavor and keeping qualities. A traditional starter needs only flour and water. If you want bread sooner, try our easy no-knead bread while your starter matures.

Troubleshooting

Hooch

A layer of grayish or brownish liquid on top of the starter is called hooch. It's alcohol produced by hungry yeast and is a sign the starter needs feeding. Pour it off (for a milder starter) or stir it in (for more tang), then feed as usual. If it appears often, feed more frequently or use a higher feeding ratio.

Mold vs normal

Normal: bubbles, a light crust or dried film on top or on the jar sides, hooch, and a tangy or yeasty smell. Scrape away any dried bits and feed.

Not normal: fuzzy spots of mold, or pink, orange or red streaks or discoloration. These indicate contamination. Don't try to scoop them out: the USDA notes that mold "roots" can run deep into soft, moist foods, which may also carry bacteria, and advises discarding moist foods with mold rather than trimming them (USDA: Molds on food). Throw the starter away, wash the jar thoroughly and start again. When in doubt, throw it out.

To prevent problems, keep the jar clean, use a clean spoon each time and keep the starter covered.

Don't taste raw starter

A starter is raw flour and water. The FDA notes that flour is a raw ingredient that can carry harmful bacteria, and advises against eating or tasting raw dough or batter (FDA: Handling flour safely). Judge your starter by sight and smell, and bake anything made with it or its discard all the way through.

No bubbles

• Too cold: move it somewhere warmer, around 75°F (24°C), such as near (not on) a warm appliance or in an oven with just the light on.
• Not enough whole grain: add some whole wheat or rye to the feedings.
• Still in the quiet phase: after the false rise, activity often drops for a few days. Keep feeding.
• Chlorinated water: try filtered or dechlorinated water.
• Old or bleached flour: use fresh, unbleached flour.

Other issues

• Smells like nail polish remover: a sign of hunger. Feed more often.
• Very runny: reduce the water slightly or use more whole-grain flour, which absorbs more water.
• Rises then collapses quickly: it's peaking fast. Use a larger feeding ratio or a cooler spot.

Next step: bake your first loaf

Once your starter doubles reliably, you're ready to bake. Our step-by-step guide on how to make sourdough bread walks you through your first loaf, from mixing and stretch-and-folds to shaping and baking in a Dutch oven.

About the author: This guide was written by the Warm Oven Bakes Editorial Team using the established flour-and-water starter method. Timelines vary with temperature, flour and water, so use the signs of readiness above rather than a fixed number of days.

Read next: How to Make Sourdough Bread (Beginner-Friendly Recipe) →