Building a sourdough starter from scratch needs exactly two ingredients: flour and water. Everything else is time and attention. This guide walks through the roughly week-long process, then hands you off to this site's own Sourdough Starter Feeding Calculator and Feeding Schedule guide once your starter is established, rather than leaving you stuck following a fixed recipe forever.

Track your progress

Check off each day as you go. Your progress is saved on this device, so you can close the tab and come back tomorrow.

Discard or no-discard: which method?

Discard

Faster, and uses less flour overall. Remove a portion of the starter at each feeding before adding fresh flour and water.

No-discard

Uses more flour overall and can take a bit longer to establish, but skips throwing anything away. Feed a small amount of starter into a larger fresh batch each day.

Both reach the same result, an active starter. This is a preference about flour use and waste, not a difference in the final outcome.

Before you start

Whole wheat or rye flour is the common recommendation for the very first mix, since whole grain flour carries more of the wild yeast and bacteria that actually get a starter going than heavily refined white flour does. You can switch to all-purpose or bread flour for the ongoing feeds after the first day or two. Use a clean glass or ceramic jar, and cover it loosely, a lid set on top without sealing, a cloth secured with a rubber band, or a coffee filter all work, since the culture needs airflow, not an airtight seal.

Days 1-2: mix and wait

Combine equal weights of flour and water, a common starting point is 50g of each, in your jar. Stir until no dry flour remains; the texture will be like thick pancake batter. Cover loosely and leave it somewhere warm, ideally 70-75°F, for 24 hours.

On day 2, just stir the mixture once to reintroduce some air. Don't add more flour or water yet. Nothing dramatic usually happens in the first two days, and that's normal, not a sign of failure. Sources genuinely differ on exactly what day 1 should look like (some start with all-purpose, some with whole wheat, some scale the amounts up or down), so treat the specific numbers here as a reasonable starting point rather than the only correct method.

Day 3 onward: discard and feed

Starting around day 3, begin a daily discard-and-feed routine: remove and discard a portion of the starter, then feed what's left with fresh flour and water in roughly equal weights. Discarding keeps the culture a manageable size and gives the remaining yeast fresh food, rather than letting the jar grow indefinitely or turn overly acidic and sluggish.

If discarding feels wasteful, a no-discard method is a legitimate alternative: instead of removing starter, you feed a small amount of it into a larger fresh batch of flour and water each day. It uses more flour overall and can take a bit longer to establish, but the end result is the same active starter.

Continue this daily rhythm through roughly day 7. Some starters are doubling reliably by then; others take closer to two weeks, especially in a cooler kitchen. A slow starter isn't necessarily a failing one, it's more often just temperature.

Signs your starter is ready

Look for consistent, reliable doubling in size within 4-8 hours of a feeding, a domed or bubbly surface, and a pleasant tangy smell rather than anything sharp or unpleasant. The float test is a quick check: drop a small spoonful in water, if it floats, there's enough gas trapped to leaven bread. If your starter smells off or looks discouraging in the first few days specifically, that's usually still early-stage competition between bacteria settling out, not a dead starter. See Sourdough Starter Troubleshooting if something looks genuinely wrong rather than just slow.

What to do once it's ready

Once your starter is doubling reliably, stop following a fixed day-by-day recipe and switch to a real feeding ratio you can maintain long-term. The Sourdough Starter Feeding Calculator works out exact flour and water amounts for whatever ratio and schedule fits your baking frequency, and the Feeding Schedule guide covers whether counter or fridge maintenance makes more sense for you. This is the actual maintenance routine you'll use going forward, not the creation recipe above.

Frequently asked questions

How long does it take to make a sourdough starter from scratch?
About 7 to 10 days for most kitchens, though it can take up to two weeks in a cooler room. The timeline depends on temperature and the wild yeast already present in your flour and environment, so a slower start isn't a sign anything's wrong.
Why does my new starter smell bad or look strange in the first few days?
This is normal. In the first day or two, a mix of bacteria (not the ones you eventually want) compete for dominance, and the smell can be genuinely unpleasant, sometimes described as similar to old gym socks or acetone. It settles down once the wild yeast and lactic acid bacteria take over, usually by day 4 or 5.
Do I need to discard starter while creating it?
Most methods discard some starter at each feeding starting around day 3, which keeps the culture a manageable size and gives the remaining yeast fresh food. A no-discard method exists too: instead of throwing part away, you feed a smaller amount into a larger fresh batch each day. Both work; discarding is faster and uses less flour overall.

How this is checked. The creation timeline and method are cross-checked against multiple independent sourdough guides, including King Arthur Baking's own official starter-creation page, rather than a single source's exact recipe. Real day-to-day amounts and starting flour choices vary meaningfully across sources, so the numbers here are presented as a reasonable, working starting point, not the single correct method. See Sources below.

Sources