This gets to the science behind baking bread. If you can make an excellent loaf of bread that turns out exactly as you want it to without knowing anything about bread hydration and baker’s percentages, great! Me? Not so much.

I started reading up on it preciesely because my bread wasn’t turning out the way I thought it should or the way I wanted to, and I figure that the best way to get my bread to turn out how I want is to learn more about the science behind it all.

Bakers percentages first.

Professional bakers express their recipes as formulas. The amount of flour always adds up to 100% and the remaining ingredients are a percentage of the total flour, and it’s always by weight, not volume. I’ll use a French bread formula as an example:

Ingredient Percentage
Flour 100%
Water 60%
Yeast 2%
Salt 2%


In this case, the hydration of the dough is 60% since that’s the percentage of water in the formula.

Another thing about the formula. Because it’s expressed as a percentage, it can be easily and quickly converted to any amount of dough – 1 pound, 10 kg, 150 pounds, 675 grams, and so on.

Here’s another example:

Ingredient Flour Water Other
White flour 650 grams 65%
Wheat flour 250 grams 25%
Water 550 grams 55%
Sourdough starter (100% hydration, so 100 grams flour + 100 grams water) 200 grams 10% 10%
Salt 20 grams 2%
Oil 25 grams 2.5%
Total 100% 65%

The sourdough starter has a hydration level of 100%, meaning that the water amount is 100% of the flour amount. That means that for every 100 grams of water in the sourdough starter, there is 100 grams of flour. Or 10 ounces of water and 10 ounces of flour. Personally, I keep my sourdough starter at 100% hydration for two reasons: one, it’s easy math if I need to convert or modify a recipe, and two, it’s easy to manage – not too thick, not too thin.

This bread has a total of 1000 grams of flour, including the flour that’s in the sourdough starter. The water amount, including the water in the sourdough starter, is 65% of the flour weight, giving this bread 65% hydration.

There are other ways of showing a baker’s formula, but I won’t go into that here. If you want to read more and totally geek out about this stuff, get Peter Reinhart’s A Bread Baker’s Apprentice.

I mentioned hydration earlier.

Hydration is a measure of how wet the dough is:

  • Stiff & Dry- 58 to 60% water content
  • Firm & Tight – 60 to 62%
  • Modestly Firm – 62 to 63%
  • Malleable – 63 to 64%
  • Soft – 64 to 65%
  • Slack – 65 to 67%

Please note that that’s water content. Oil or other fats don’t count towards hydration.

American style breads usually are about 60 to 62% hydration, French style breads between 62 to 65%, and Italian style (ciabatta) breads upwards of a 68% range.

I calculated Peter Reinhart’s bagel recipe – converted to grams, so there may be rounding differences – to be around 52% hydration. In kneading it, it required zero added flour and did not stick to anything – not my counter, not my hands, nothing. I knew this was likely the case walking in because I’d calculated the hydration levels first.

Another recipe I’ve made I calculated the hydration levels as 65-67% but the recipe had a description that the dough should be tacky, not sticky. I already know that 65-67% will definitely be sticky (this could also be because of my heat and humidity levels), so I wasn’t surprised that a whole bunch more flour was added before the proper description of feel was achieved. My ending hydration levels were closer to the 58% hydration level.

About humidity – I live in the tropics and we’re currently in monsoon season (we have two). That means that the humidity levels here are significantly higher. Since flour and other ingredients can absorb water from the air around us, I may need higher amounts of flour/less liquids in a recipe to achieve the exact same feel in the dough as compared to someone from, say, Edmonton, Alberta, or Phoenix, Arizona. So if you tell me that you make the exact same recipe as me, but your hydration levels are different than mine even though ours turned out the same, I’m okay with that. And I would expect that. 🙂 And this is all on top of different flours absorbing different amounts of water differently.

And that’s something else that calculating hydration levels and the dough formula does for me – it tells me what to expect from the dough. Is the description for the dough saying it should be firm and tight but the calculated hydration levels tell me soft, or vice versa? I already have a clue, right there, that the amount of flour or water used will have to be altered.

In the end, when making bread, I record the ending flour amounts I actually used so that, next time, I can start out a whole lot closer so I don’t have to do as much jimmying with the recipe each time. It’s easier for me and it’s easier to get more predictable results from my bread. And, to me, that’s what baker’s percentages and hydration levels do for me – they allow me to get predictable results.

[pg-image src=”” link=”” caption=”bread dough, 67 percent hydration” alt=””] [pg-image src=”” link=”” caption=”bread dough, 54 percent hydration” alt=””]

13 Replies to “Baker’s Percentages and Bread Hydration”

  1. Pingback: Sour Flour » Blog Archive » Baker’s Math
  2. Searching for whether eggs in sourdough count towards hydration I came across this site – didn’t find what I was looking for, but have a question: I was always under the impression that the flour in the SD doesn’t count toward baker % .
    Right or wrong?

  3. Eberhard, it’s neither right nor wrong. There are multiple ways that bakers calculate hydration.

    With eggs, if you want to count them towards hydration (and if you want to be nitpicky, you would, but it’s one of those either/or what do you feel like kind of things), then you would use 75% of their weight as water, the other 25% is solids.

    With the flour and the water in the sourdough starter, it’s again one of those what do you feel like scenarios. Some people count it, some people don’t. But if you’re going to count the flour in the hydration calculation, then you must also count the water in the hydration calculation.

  4. what a useful and clear explanation. have you ever thought of making mozzarella in sri-lanka? all that buffalo milk around, someone should. you’d be well set up for pizza then x

  5. Tom, I have considered making mozza. However, it requires fairly consistent and specific temperatures which would require me buying a separate fridge or some such thing, and that’s just not practical. Also, we’ve recently relocated to Singapore where cheeses, real cheeses, are actually available & good. 🙂

  6. Hi, I just wanted to suggest that you can getaway with using 1.1% yeast instead of 2%. It was recommended on King Arthur Flour website. I’ve also read somewhere that overpopulation of yeast is not good for the bread–the less yeast the better. I’ve been baking bread now for 2 years and been using 1.1% recommendation and it works like a charm. I make dough in 5-pound batches.

  7. Ramin, your 1.1% of yeast instead of 2% sounds entirely reasonable. I make bread exclusively with wild yeast, aka sourdough starter, so I am no expert at anything related to commercial yeast, so I appreciate your input. 🙂

  8. I have been baking all kinds of breads for many years with varying degrees of success. I watched Peter Reinhart’s Perfect Pizza video and for the first time, my pizza turned out just as I would like it to. So I signed up for his Artisan Bread course and started watching today. It’s the first time I’ve heard of baker’s math, I can hardly believe it. You have a fine explanation of the percentages and I appreciate that you have posted it. It’s midnight here just north of Chicago, so tomorrow I will take a look again with a clear head. Thanks again! Joanna

  9. So, I know this is a very old post, but I still don’t quite get how to actually do the conversion to use a 100% hydration starter (which is how I keep mine as well) in recipes like, say, many of Reinhart’s that use a 66% hydration starter. Do I calculate the difference in flour and water and then add more or less to the starter/pre-ferment or do I make that adjustment when making the main dough? Or does it matter? So confusing.

  10. Let me see if I understand you…

    Using a sample recipe:

    Ingredients for the SF Style Sourdough

    233 g Starter (66% hydration)
    264 g bread flour
    50 g spelt flour (pref. whole grain)
    204 g water
    9 g salt

    If I understand you correctly, here’s how I would tackle it.

    233 g starter at 66% hydration = 140 g flour and 93 g water.

    But you want to use your 100% hydration starter instead of his 66% hydration starter. I would leave the flour portion of that starter the same – 140 g – and increase the water portion to match – 140 g – so that the resulting starter would be 280 g. I would then decrease the amount of water by the difference (140g-93g=53g), so the amount of water I would use would be 204g-53g=151g.

    So my revised ingredient list would look like this:

    280 g Starter (100% hydration)
    264 g bread flour
    50 g spelt flour (pref. whole grain)
    151 g water
    9 g salt

    I left the amount of the fermented flour the same as in the original recipe and just adjusted the water as needed. The amount of fermented flour is more important since that’s your leaven. The amount of water in the recipe is easy to adjust so that the net amount remains the same.

    I hope this helps. 🙂

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