How to Make a Sourdough Starter from Scratch

A day-by-day guide · Updated July 2026

There's something magical about creating life from just flour and water. Over the next 7–10 days, a simple mixture turns into a bubbling culture that can raise bread for years. This guide gives you exact amounts, temperatures and the signs to watch for at every stage.

What you'll need

• Strong bread flour (12.5–13% protein works best)
• Room-temperature water, ideally dechlorinated (see our hydration guide for why chlorine matters)
• A clean jar with the lid resting loosely on top
• A kitchen scale — starters live and die by grams, not cups
• A warm spot: 80–83°F / 27–28°C for the first days

Day 1: the initial mix

Mix 50 g flour with 50 g water until no dry flour remains — it should look like thick pancake batter. Keep it warm (80–83°F / 27–28°C), covered with the lid slightly ajar so gases can escape. Twelve hours later, give it a good stir. It will feel runny and show no activity yet; both are normal.

Day 2: first feedings

Keep 50 g of the mixture, discard the rest, and feed it 50 g flour + 50 g water. Hold the warm temperature and stir once after 5–6 hours. Repeat the same feeding about 12 hours later.

You might see a few bubbles, or nothing at all. The smell may turn a bit funky or unpleasant around now — that's actually a good sign. The culture is establishing itself.

Days 3–4: cool it down and build momentum

Now the routine changes: keep 40 g of starter and feed 40 g flour + 40 g water every 12 hours, but at a slightly cooler 75–76°F / 24–25°C. Stir 5–6 hours after each feed.

Starting warm jumpstarts activity; cooling down favors the yeast and bacteria you actually want. By day 4 you should see real evidence of life: surface bubbles, some rise, maybe a ring on the jar marking where it rose and fell.

Days 5–7: growing stronger

When you see lots of bubbles and a clear rise-and-fall pattern, your starter is gaining strength. The texture stops being runny and develops body; the smell shifts toward fermented fruit. From this point:

• Feed every 12 hours at 1:1:1 (40 g starter : 40 g flour : 40 g water)
• Stay at 75–76°F / 24–25°C
• When you stir, fold the edge over the top — a "mini stretch and fold" that builds structure

Days 7–10: increase the food

Once it rises consistently, your starter is ready for bigger meals. Feed 20 g starter with 40 g flour + 40 g water (a 1:2:2 ratio). If it rises and collapses well before the next feed, increase the food again. Work up gradually — a young starter drowns in too much food at once.

You're looking for a starter that triples in volume, holds a domed top, and smells pleasantly fruity. That high point is called the peak — knowing how to catch it is the single most useful skill in sourdough, and we cover it in When Is Your Starter at Peak?

Troubleshooting the first two weeks

• Activity vanished around day 3–4. Normal. The early bacterial party fades before real fermentation kicks in. Keep feeding on schedule.
• Soapy-looking bubbles. Too warm or too hungry — lower the temperature slightly or feed more.
• Nothing after a week. Check your water (chlorine suppresses yeast) and your temperature. Cold kitchens can double the timeline.
• Comparing timelines. Don't. Some starters take 7 days, others 14. Environment matters enormously; trust the signs, not the calendar.