‘Dude, what’s the hydration?’

So, if you’re on Instagram or Facebook or anywhere people can post bread pics, then you’ll have noticed that no comments section is complete without someone asking, ‘What’s the hydration on that?’. If you’re new to sourdough baking or you’ve just been sticking to one recipe, then you may not know what hydration is, or why it matters, or if in fact it does matter at all. Well let me explain.

Quite simply, the hydration of a dough is the amount of water (liquid) in relation to the total amount of flour, expressed as a percentage. Now here we might just need to step back and clarify bakers’ maths. In commercial bread baking, recipes are given as formulas, with everything listed as a percentage of the total flour. This makes it much easier for a baker to scale any dough formula up or down depending how many loaves they want to bake. So, the total amount of flour in a recipe is always 100% and the other ingredients are given as a proportion of it. Let’s look at a basic non-sourdough recipe to get an understanding of this:

1000g Strong White Flour 100%

650g Water 65%

20g Salt 2%

15g Instant Yeast 1.5%

In this example, the hydration of the dough is 65%. To calculate this, we divide the total weight of the water (650) by the total weight of the flour (1000) and then multiply the answer by 100 to convert it into a percentage: 650/1000 = 0.65 x 100 = 65%

Now if this was a recipe you used every weekend to bake your weekly bread and you were happy with the results, then there would probably be no need to work out or understand the hydration of the dough. As far as you’re concerned, it works and you’re happy. However, if you wanted to make a little extra one week or you were using up some flour to clear out the cupboard, you could use the bakers’ maths to upscale the formula.

For this example, let’s say we weighed out our flour and it came to 1250 grams, how much water would we need to replicate the 65% hydration dough from our weekly bake above? We would divide the total weight of flour (1250) by 100 and then multiply the answer by 65 (the hydration percentage we are aiming for) giving us an answer of 812.5g of water:

1250/100 = 12.5 x 65 = 812.5g

1250g Strong White Flour

812.5g Water

You can then use the formula to work out the remaining ingredients:

25g Salt (1250/100 = 12.5 x 2= 25g)

18.75g Instant Yeast (1250/100 = 12.5 x1.5 = 18.75g)

Now let’s say you wanted to use this flour to make a pizza base or a foccacia, you might want a slightly slacker, wetter dough, so you could use the bakers’ maths to work out how much water you would need to take this dough up to 75% hydration. (1250/100 = 12.5 x 75 = 937.5g). Note the amount of salt and yeast wouldn’t change, they are still 2 and 1.5% of the total flour weight, so the new recipe would look like this:

1250g Strong White Flour

937.5g Water

25g Salt

18.75g Instant Yeast

You can also use the bakers’ maths to calculate the weight of the ingredients for a specific amount of dough. If you have a 900g loaf tin for instance, you can work out how much flour you will need by adding all the percentages in the formula together, dividing the answer by 100 and then dividing your required dough weight by that answer. Sounds complicated but let’s work it out using this example:

Flour 100%

Water 65%

Salt 2%

Yeast 1.5%

100 + 65 + 2 + 1.5 = 168.5/100 = 1.69

900/1.69 = 532.5

So, to make 900g of dough at 65% hydration, you would need 532.5g of flour, depending how much of a stickler you are for accuracy, you could round that up to 533g. You can now use the original formula to work out the remaining ingredients:

100% Strong White Flour 533g

65% Water 347g

2% Salt 10.7g

1.5% Instant Yeast 8g

When it comes to sourdough, things get a little more complicated as we must account for the flour and water in our leaven. Not all recipes do, but they should give you some indication as to whether this is the case or not. This is where you’ll also discover the benefits of maintaining your starter at 100% hydration, as it allows you to easily calculate the weight of the flour and the water in it i.e. half the weight of the leaven is flour and half is water. So, let’s look at the recipe below and work out what hydration it is. To make it a little more fun, I’ve included two types of flour:

80g Leaven (100% hydration)

350g Strong White flour

50g Rye Flour

300g Water

9g Salt

The first thing we need to work out is the total amount of flour:

40g from the leaven, 350g Strong White and 50g Rye = 440g total flour

Then we need to work out the total amount of water:

40g from the leaven and 300g water = 340g total water

So, to calculate the hydration of this dough, we would use the following formula:

340/440 = 0.77 x 100 = 77%. So, the hydration of this loaf is 77%.

Now, if you made this loaf but felt the dough was a little wet and not holding its shape quite as you wanted, you might choose to lower the hydration to 75% the next time you baked it. The formula to calculate this would be: 440/100 = 4.4 x 75 = 330g water. But remember, this is the total water, so includes that from the leaven. We now need to deduct 40g (half the weight of the leaven) to account for this: 330 – 40 = 290. So, to make this dough at 75% hydration you would need 290g water.


So, that’s bakers maths and hydration, but is it important? Why are people so obsessed with it? Well there’s a number of reasons. Technical ones; flour absorption, type of bread being made, desired crumb texture, and bravado ones; look at me, I can handle an 85% hydration dough! As with everything in life, there is a certain level of competitiveness in baking (someone should make a TV show about that!). There is also a fallacy, particularly amongst new sourdough bakers, that in order to achieve an open crumb with big air pockets, you need to have a ridiculously high hydration dough. There is some truth to this, but it’s a dangerous mindset to get into when just starting out. It’s all too easy to bake a flat, dense loaf and think the solution to opening it up is to increase the hydration next time.

But believe me, if you carry on down this route, you’ll find yourself in a never-ending spiral of heavy, gummy loaves and eventually the frustration of throwing away frisbee after frisbee will become overwhelming and you’ll just give up. My advice is always to start low, 65 even 60% hydration and then build your way up as your skill and confidence grows. If you’re just starting out it’s unlikely that a dense loaf is the result of too lower a hydration, you’d be much wiser to look at your starter activity and bulk fermentation process for the solution.

So that’s my thoughts on hydration! You can obsess over it and push it as high as you want if that’s what floats your boat, but for me, it’s an afterthought, the consequence of testing, practicing and honing a recipe. Once I’m happy with a particular bread and I’m getting consistent results, I will calculate the formula and add it to my collection. Whether it turns out to be 65% or 85% hydration is irrelevant, it’s good bread that I’m after and that’s judged by texture and taste, not by a calculator!

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