How to Tell When Your Sourdough Starter Is Ready to Bake With

Your sourdough starter is ready to bake with when it has doubled in size, is bubbly all the way through, smells yeasty and a little tangy, and passes the float test. That usually happens 6 to 8 hours after a feeding, depending on your temperature and hydration. If your jar is missing one of those signs, it most likely needs a little more time, warmth or another feeding.

When I started, I had absolutely no idea what I was doing. How hard could it be to tell when a jar of flour and water is ready? Turns out, pretty hard. Here's how to read your starter and what to do when it isn't there yet.

The three signs your starter is ready

In my book I describe what a healthy starter looks like in three parts: bubbles, a rise and fall, and a tangy aroma. When a starter is ready to bake with, all three show up at once.

It has doubled. Your starter should be roughly twice as tall as it was right after you fed it. My book's glossary calls this an "active starter": bubbly, doubled in size and ready to be used in baking.

It's bubbly all the way through. Bubbles mean active fermentation. Check the sides of a clear jar too, since a ready starter has bubbles throughout and not only on the surface.

It smells yeasty and slightly sour. A yeasty, slightly sour smell is ideal. This is the tang that ends up in your bread, thanks to the bacteria in that little community of wild yeast and friendly bacteria.

Use a rubber band so you can see the rise

How do you know it doubled if you can't remember where it started? You mark it. One of my pro tips in the book is to mark the jar with a rubber band or a dry-erase marker so you can track your starter's rise and fall.

Right after you feed, stir it, wrap a rubber band around the jar at the level of the starter, and set the lid on loose. That's my routine every time: 15 to 30 grams of starter (I usually use 30), 100 grams of room temperature water, 70 grams of bread flour and 30 grams of rye, a rubber band at the line, and then I leave it for 6 to 8 hours.

Once the top of the starter has climbed to twice the height of that rubber band, you have your doubling. The rubber band does the remembering for you.

The float test, done gently

The float test is the third check in my book. My glossary describes it as placing a small amount of starter in water: if it floats, it's active.

Fill a glass or small bowl with water, then take a small spoonful from the top of the jar and let it rest on the water. The book's version is one line: if it floats, it's active.

If it floats, it's full of gas and ready to go. If it sinks, check the jar again. Is it doubled? Is it bubbly? Treat the float test as one more clue next to the doubling and the bubbles, because the FAQ in my book lists all three together: bubbly, doubled and floating.

Timing: the peak, and what past peak looks like

Your starter rises after a feeding, reaches a peak, and then falls. That rise and fall is the cycle my book says shows your starter is thriving, and the top of the rise is the moment you want to bake.

Expect 6 to 8 hours after a feeding. Treat that number as a starting point and let the jar tell you. I give it that full stretch and keep an eye on the rubber band.

Past peak looks like this: the starter has risen, and then it settles back down, so the top sits lower than your highest mark. It's still alive, and it simply finished its meal. In the book I mention that as long as you feed after it has hit its peak, you're good to go.

Getting a starter ready after the fridge

Mine lives in the fridge most of the week, so this is the situation I think about most. My book's routine for infrequent bakers is simple: once you're ready to bake, pull it out the day before, discard and feed.

Whether it needs a feed the moment it comes out depends on when it went in. If you fed it and put it straight in the fridge, it will usually rise on that feed once it warms up. If it went in after it had already peaked and fallen, feed it right out of the fridge. Either way, watch the rubber band and the three signs, not the clock.

There's a trend of baking with starter straight from the fridge. I haven't tried it, so I can't speak to it, but feel free to explore! The full fridge routine is in how to store sourdough starter in the fridge.

If your starter isn't ready yet

Most of the time, a starter that isn't ready is just early, or cool. Here's what I'd try, in this order.

Give it a warmer spot. Starters thrive in a warm spot around 70 to 75°F; on top of the fridge works. My book says that if your home runs colder, you can keep your starter in the oven with the oven turned off, and I've even turned the oven light on for a little added heat. Take the jar out of the oven BEFORE you use the oven, because I've seen and heard many horror stories.

Try warmer water at the next feeding. The warmer the water, the faster the starter rises. Aim for 85 degrees while you're building a starter. Going over 90 to 100 degrees can scorch your flour.

Give it a little more time. I used to obsess over my starter's temperature, then realized it mostly matters when I'm trying to get it ready to bake. If the jar is warm and the band hasn't moved, give it a little longer and check again.

Feed it again. If it has peaked, fallen and still hasn't done much, discard down and feed it fresh flour and water, then give it another round. Starters can take a few days to bounce back.

If it's flat after all of that, with no bubbles and no rise, you're asking a different question, and I wrote a whole guide for that: is my sourdough starter dead?. In my personal opinion, the only time you absolutely have to restart is mold. And if you want a refresher on the feeding ratio itself, it's in how to feed a sourdough starter.

Quick answers

How long does it take for a starter to be ready after feeding? About 6 to 8 hours is typical, depending on temperature and hydration.

Does my starter have to pass the float test? It's a helpful check, and my book lists it alongside bubbly and doubled in size. If it's doubled and bubbly but sinks, look again at the jar and try another feeding.

Can I bake with a starter that has already fallen? It has finished the best part of its rise, so I'd feed it and wait for the next peak. That gives your bread the strongest start.

Bake it anyway

Sourdough has taught me a heck of a lot about patience, grace and how to laugh things off. Your first loaf may not be perfect, and mine certainly wasn't (not pictured). Bake it anyway.

If you want to know at a glance whether your jar is ready, hungry or in trouble, my "Is My Starter Okay?" cheat sheet ($5.99 in the SourdoughKitchenShop on Etsy, linked here) puts every symptom, cause and fix in one table, plus a fridge-door page you can check before you reach for the flour.