The Fresh Loaf

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Help to convert starter hydration from volume to weight

bakerincanada's picture

Help to convert starter hydration from volume to weight

Hi everyone I have been perusing the northwest sourdough sites and want to try out a recipe.  The recipe calls for 3 cups of 166% hydration starter (equal volume of flour and water).  Can someone please convert this to % hydration by weight as this is how I do it.  I currently  have one starter at 100% hydration by weight and the other 60% hydration by weight.  This is where the recipe is found . If any one can help me out I would really appreciate it the math is stumping me this morning. Thaks Bakerincanada.

bakerincanada's picture


Oops the post above I sent it before I commented.  I keep thinking about my question and maybe it is a silly one.  For those experienced bakers out there - maybe the % hydration is the same regardless whether you use volume or weights.  Any comments would be appreciated.  I see in another post from qahtan that I am not the only one who gets confused.  Thank goodness.  Baker in canada

pmccool's picture

Your question isn't silly at all.  Bakers percentage is always based on weight, never on volume.  The base assumption is that the weight of all of the flour in a formula is 100%.  Doesn't matter if it is 28 ounces, 5 kilograms, or 150 pounds.  Whatever the flour weighs, that's 100%. 

Hydration, also expressed in percentage, is the weight of liquid relative to the weight of the flour.  So, if your formula calls for 16 ounces of flour and 10 ounces of water, the percent hydration is 10/16 = 0.625 = 62.5%.  A really stiff bagel dough might be less than 60%.  A really soupy ciabatta dough might be around 90% hydration. 

The reason it matters is that we each come up with varying weights of flour in our volume measurement.  If I fluff the flour and gently spoon it into a cup, I might wind up with 4 to 4.5 ounces of flour.  If you scoop up a cup of flour by digging it into your canister, you might come up with 6 or 7 ounces of flour.  If each of us then combines our "cup" of flour with a cup of water (which will always weigh 8 ounces), I'll have a thin batter and you'll have a either a very thick batter or a very wet, gloppy dough.  In bakers percentages, mine will have about a 200% hydration (8 ounces water / 4 ounces flour)and yours will have about 120% hydration (8 ounces water / 6.5 ounces flour). 

In the example above, both of us would have achieved 100% hydration (1 cup of water to 1 cup of flour) on a volume basis, but the result would have been very different than what either of us (or the recipe writer) intended.

By using bakers percentages, which are based on weight, it is a lot easier to get consistent results with our baking.  Took me a while to catch on to the concept, since I was brought up using volume measurements, but I love my scale now.

Hope that helps.


mcs's picture

6.7 oz more water + 20.3 oz 100% starter = 27 oz starter at 166%

On the recipe that you're referring to, as explained in the above post, by telling you the hydration level, 166%, they are saying that you have 1.66 times as much water in the starter as you do flour. The cup measurements are irrelevant if you'll be talking about hydration %.

So if you wanted to use your 100% starter for this (and you have enough of it) to make it 166%, you would add 66% (2/3) more water to your already existing starter. For example to make 27 oz., you would need to increase the water by 66% in your existing starter.

In 20.3 oz, your 100% starter has 10.15 oz. of water already. Add another 6.7 oz of water, and you get 16.85 oz. water / 10.15 oz. flour = 1.66 (166% hydration) and 27 total oz.

If you don't have enough starter, you could probably create a poolish with the same proportions and just go to 16.7 oz water + 10.3 oz flour = 27 oz. poolish  and call that your starter. 


bakerincanada's picture


Thank you both for your feedback regarding hydration.  After the first post I made I had convinced myself that bakers percents were based on weight.  Anyway I was glad to get the confirmation and some of the theory behind it.  I use the scale all of the time and yes weights are much easier.  I think that's were I got threw off when the recipe started talking about volumes.  Anway I do appreciate the feedback.  It is so nice to be able to ask questions on line.  Otherwise I probably would have been still stewing about whether I was right or not.

baker in canada

JessicaT's picture

Sorry to unearth a SUUUUUPPERRR old thread. I am looking at the Norwich Sourdough bread recipe, and it calls for 100% hydration, would this mean that I would add equal portions of flour and water by weight? I currently have a starter going, but feed it by volume and not weight. Help?