The float test for yeast dough and sourdough starter: Does it really work?

How do you know when your yeast dough has fully risen? And what about sourdough starter? You feed it and it grows and bubbles for hours, but when is it actually at its baking peak? Many claim dropping a bit of dough or starter into water to see if it floats answers both these questions. But we weren’t convinced — so we did our own float test to find out.

How does the float test work?

Here’s the deal. As the yeast in dough or starter works, it produces tiny bubbles of carbon dioxide. This CO₂, trapped within the glutenous web formed by flour and liquid, makes dough or starter (or an overnight preferment) rise, lightening its consistency in the process.

The float test: fact or fiction? Find out if floating yeast dough in water is truly a good way to judge whether it's fully risen. Click To Tweet

Float test for yeast dough sourdough starter via @kingarthurflour

Let’s do the float test

Yeast dough that’s just begun to rise sinks like the proverbial stone when dropped into water. Float test for yeast dough sourdough starter via @kingarthurflour

But the longer it rises, the more gas is trapped until eventually the dough becomes lighter than water and floats.

So far so good. Yes, fully risen dough will float when placed in water.

Float test fail: false positives

But this test doesn’t go far enough. What about dough that’s not at its peak? Will it remain submerged in water, or pop to the top?Float test for yeast dough sourdough starter via @kingarthurflour


This is called a false positive: the test result points one way, but the reality is actually something quite different.

I’m using my favorite pain de mie dough for these tests. The recipe calls for the dough to rise for 60 to 90 minutes, until it’s nice and puffy.

The dough above has risen for 30 minutes and is just beginning to climb the sides of the measuring cup. Clearly, it isn’t anywhere near “nice and puffy.” Yet when I place a small scoopful in water, it rises right to the top and stays there.

Float test for yeast dough sourdough starter via @kingarthurflour

What about sourdough starter?

After being refrigerated without feeding for several weeks, my sourdough starter is clearly in need of attention. So I feed it and drop a bit in some water. As expected, it sinks.Float test for yeast dough sourdough starter via @kingarthurflour

Here’s the starter 4 hours later. Note how the bowl of fed starter shows only a few small bubbles; I’d estimate it has at least 2 to 4 hours to go before it’ll be suitable for baking. Yet the starter dropped into water rises right to the top.

So is the float test a good way to assess the rise of yeast dough or baking readiness of sourdough starter?


Both partially risen yeast dough and growing (but not yet ripe) starter will float in water.

Your takeaway

If rising yeast dough or fed sourdough starter sinks in water, it’s definitely not ready to continue to the next step in your recipe.

But just because either floats doesn’t necessarily mean they’re good to go.

Best way to tell if your dough is fully risen? Poke it with your index finger. If the indentation remains, it’s ready to go. If the dough rebounds and your finger mark disappears, it needs more time.

What are the signs of a perfectly ripe starter? It’s very bubbly, and is reliably doubling in size within 6 to 8 hours of feeding.

Want to learn more about rising yeast dough? Read our blog post, The bread also rises. For more information about starter, see our sourdough baking guide.

PJ Hamel

PJ Hamel grew up in New England, graduated from Brown University, and was a Maine journalist before joining King Arthur Flour in 1990. PJ bakes and writes from her home on Cape Cod, where she enjoys beach-walking, her husband, two dogs, and really good food!


  1. Ralph Douglas

    I’m not sure about this flaot test any more, my starter is quite active bubble wise but sinks in water however the loaves come out beautifully.

    1. The Baker's Hotline

      Hi there, Ralph! While the float test can be a helpful indicator we found that it isn’t definitive. When it comes to telling if your starter is ripe, we still like to see that the starter is bubbly and reliably doubles in size within 6 to 8 hours of being fed. Kindly, Morgan@KAF

  2. Rosa oh

    Hello. So if my starter does not float, what should i do? Should i wait more and keep it on countertop? Or throwaway…? 🙁

    1. Rosa oh

      Oh my….. thank you so much for the reply!! I didnt expect! The article you mentioned is really helpful!
      Thank u so much. I love the King arthur flour and the website has so much information for me to improve sour dough and etc. Have a splendid day!

  3. Joellyn Jaeger

    Regardless of where your sourdough starter came from, within a month or so it will become the starter from your region, as it picks up local yeast spores from your locality. So, no matter how a starter sent from San Francisco tastes when it first arrives, in time it will develop it’s own flavor and may be very different from the original. Food, or yeast, for thought.

    1. The Baker's Hotline

      Hi Frauke! Are you using a recipe? If so, would you mind sharing a link with us? We’d be interested in knowing what kind of adjustments you’re referring to. Annabelle@KAF

  4. Betty Holmes

    I just tried your no knead sour dough bread yesterday. It took a lot of time but it was the first time I had such wonderful results. Interestingly after 50 plus years of making various breads I found the process very educational. The most amazing experience was the actual texture of the dough, I knew it was going to work. Thank you!
    PS it was also a nice cool rainy day which I have found always makes the bread better

  5. Nola Beckum

    I have a different situation with starter that most people have and because of this, I can’t go by what starter fermenting or rising times other experience. I live in TN, and my 102 yr old house has no heat and no AC in summer months. As I type this, there is snow on the ground and an outside temp of 25F, so my house is cold! I just fed my starter about 15 min ago and there are a few bubbles forming on the surface in the KA crock I use. If it behaves as it usually does, it will begin rising and maybe by tomorrow around noon, maybe shortly before, it could be at the top rim of the crock, but I doubt it’s ready. My starter doesn’t fall and stirring it doesn’t cause it to fall, but it’s always nice and thick. So … it’s very difficult for me to “guess” when it’s ready for making bread, but that’s what I have to do … guess. The floating test doesn’t work. I wonder if anyone else has to rely on guessing. I would LOVE for my starter to “talk” to me or give consistent signs, letting me know if it’s ready.

    1. Joellyn Jaeger

      I keep mine in the fridge if baking a large batch of bread once a week and it is always ready. If doing more baking (crackers, etc.), I use it, I feed it, leave it out until bedtime, and then refrigerate until early AM. Take it out early morning, and it should be ready to go when it warms a bit. I can let mine go without being fed for a week if kept in the fridge. And mine is more of a “polish” starter than a “biga”. The smell is the key for me. If it is mild, it is not ready. Started my own many years ago, and it has not failed yet.

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