Bread flour is the most reliable choice for sourdough, but all-purpose flour works too

Bread flour is your best option because it has 12 to 14 percent protein, which builds strong gluten networks that trap gas and create an open crumb structure. All-purpose flour (10 to 12 percent protein) will also produce good sourdough, though the texture may be slightly denser. The difference matters most if you are aiming for large, irregular holes in the finished loaf. Whole wheat, rye, and spelt flours can be mixed in at 10 to 30 percent of your total flour weight without replacing bread flour entirely—they add flavor and nutrition but weaken the gluten structure if used alone.

The protein percentage is printed on most flour bags under "nutrition facts" or listed on the manufacturer's website. King Arthur Baking Company, Bob's Red Mill, and Gold Medal all publish these numbers. If you cannot find the protein content, bread flour labeled "bread flour" will almost always be higher protein than "all-purpose flour," regardless of brand.

Key Takeaways

  • Bread flour (12 to 14 percent protein) produces the most open crumb and is the standard choice for sourdough.
  • All-purpose flour works and will produce acceptable sourdough, though the crumb may be tighter and less airy.
  • Whole wheat and rye flours add flavor but should not exceed 30 percent of your total flour weight, or gluten development suffers.
  • Check the nutrition label or manufacturer's website for protein content if you are choosing between brands.
  • Bleached and unbleached bread flour perform identically in sourdough—the choice is personal preference.

Why protein percentage matters in sourdough

Protein forms gluten when it hydrates and is worked by mixing or folding. Sourdough relies on long fermentation (8 to 48 hours) rather than commercial yeast to rise, so strong gluten is essential—it must hold gas bubbles for the entire fermentation without collapsing. Bread flour's higher protein count means more gluten can develop, and that gluten stays elastic longer under the stress of fermentation.

All-purpose flour has less protein, so it develops gluten more slowly and cannot hold as much gas. The result is a denser crumb with smaller, more uniform holes. This is not a failure—many bakers prefer this texture—but it is a visible difference. If you are using all-purpose flour, expect a tighter loaf and adjust your expectations accordingly.

Whole wheat, rye, and specialty flours

Whole wheat flour contains the bran and germ of the wheat kernel, which are harder and sharper than the starchy endosperm. These particles cut gluten strands as you mix and fold, weakening the network. Rye flour behaves similarly but also absorbs more water, making the dough wetter and harder to handle. Both add nutty, complex flavors that many sourdough bakers love.

Use whole wheat or rye at 10 to 30 percent of your total flour weight—for example, 150 grams of whole wheat and 850 grams of bread flour in a 1000-gram loaf. This keeps gluten development strong while adding flavor. Going above 30 percent requires adjusting your hydration (adding more water) and extending fermentation time, which is possible but demands experience. Spelt, einkorn, and other heritage grains work the same way: use them as a portion of the total flour, not as a replacement.

Bleached versus unbleached bread flour

Bleached flour has been treated with chlorine gas or benzoyl peroxide to whiten it and slightly strengthen gluten. Unbleached flour is aged naturally over weeks, which also strengthens gluten but more slowly. In sourdough, the difference is negligible because fermentation time is so long—the gluten develops fully either way. Both will produce excellent bread.

The choice comes down to personal preference and what your local stores stock. Some bakers prefer unbleached for the perception of less processing, while others find bleached flour more consistent batch to batch. For sourdough, either is fine.

How to adjust your recipe if you switch flours

If you move from bread flour to all-purpose flour, your dough will be slightly stiffer because all-purpose absorbs less water. Start with the same hydration percentage (for example, 75 percent water to flour by weight) and mix as usual. If the dough feels too dry after 10 minutes, add water 5 milliliters at a time until it reaches the texture you want. The finished loaf will be denser, but the process is otherwise identical.

If you are adding whole wheat or rye flour, increase your water by 5 to 10 percent of the total flour weight. Whole wheat absorbs more water than white flour, so a dough that felt right with all bread flour will feel too stiff once you swap in 20 percent whole wheat. For example, if your recipe calls for 750 grams of bread flour and 250 grams of water (33 percent hydration), and you switch to 600 grams of bread flour plus 150 grams of whole wheat, add 250 to 275 grams of water instead of 250.

Storage and freshness

Bread flour stays fresh for 6 to 8 months in a cool, dry cupboard. Whole wheat flour goes rancid faster—usually within 3 to 4 months—because the oils in the bran oxidize. Store whole wheat flour in the refrigerator or freezer if you do not use it regularly. All-purpose flour has a shelf life similar to bread flour.

Stale flour (especially whole wheat) can produce a slightly sour or off taste in your sourdough. If your flour has been open for more than a few months and smells musty or sour, replace it. Sealed bags last longer than opened ones.

Common mistakes when choosing flour

The most common mistake is using cake flour or pastry flour, which have 7 to 9 percent protein. These are too soft for sourdough and will produce a gummy, collapsed loaf. Cake flour is labeled clearly, so this is straightforward to avoid—just check the bag.

Another mistake is assuming all-purpose flour and bread flour are interchangeable without adjustment. They are close, but all-purpose is noticeably lower protein. If your sourdough recipe was written for bread flour and you switch to all-purpose, expect a denser result and do not assume something went wrong with your technique.

A third mistake is adding too much whole wheat or rye flour at once. Many new bakers want to use 50 percent whole wheat for flavor and are surprised when the dough collapses during fermentation. Start at 10 to 15 percent, bake a loaf, and increase gradually if you want more whole grain flavor.

Frequently Asked Questions

Can I use self-rising flour for sourdough?

No. Self-rising flour contains salt and baking powder, which will interfere with fermentation and make your sourdough taste wrong. Use only bread flour, all-purpose flour, or specialty flours without added ingredients.

What if I cannot find bread flour at my store?

All-purpose flour will work. Your loaf will be denser and have smaller holes, but it will still be good sourdough. If you have access to online ordering, King Arthur Baking Company and Bob's Red Mill ship to most addresses. Local bakeries sometimes sell flour by the pound and may stock bread flour even if grocery stores do not.

Is there a difference between bread flour brands?

Protein content varies slightly—King Arthur is typically 12.7 percent, Gold Medal around 12.5 percent, and store brands often 12 to 12.5 percent. These differences are small enough that you will not notice them in the finished loaf. Pick whichever is available and affordable.

Can I mix different flours in the same loaf?

Yes. Many sourdough bakers use 80 percent bread flour, 10 percent whole wheat, and 10 percent rye for complexity. Mix the flours together before adding water, so they hydrate evenly. The total protein percentage will be lower than pure bread flour, but the gluten will still develop adequately.

Do I need to sift flour before measuring?

No. Sifting aerates flour and changes how much fits in a cup, which can throw off your ratios. If you are measuring by weight (grams), sifting makes no difference. If you are measuring by volume (cups), sifting will make your measurements less accurate for sourdough, where precision matters. Weigh your flour instead.