If you are new to sourdough, it’s important to first get your head around ratios and percentages, as they are critical to the fundamentals of baking bread. The weight people give in grams for a particular recipe is largely unimportant, as it is specific to them and their schedule, conditions, preferences, etc. The ratios in the formula are the important part.

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RATIOS

For instance, if you see starter instructions that call for 100g flour and 100g water to feed, the total weight is irrelevant. What’s important is this is a 1:1 ratio. Taking that a step further, the next important ratio is the amount of starter you add to the flour and water when feeding. If you are adding an equal weight of flour and water at feeding, then you are following a 1:1:1 ratio.

60g starter + 60g flour + 60g water = 180g total weight

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This 1:1:1 ratio is perfect when you are first developing a new starter and for quick, successive feeds - it is considered a lower ratio feed (high inoculation rate). For ongoing maintenance at room temperature, an established starter is often fed at a higher ratio (low inoculation rate) so that it requires less feeding and keeps acidity in check. This means it needs feeding less often as well. Here are some example feedings: 

50g starter + 100g flour + 100g water = 250g total weight (1:2:2)

40g starter + 120g flour + 120g water = 280g total weight (1:3:3)

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Notice that I’ve used different starting weights for each example. This is because the only thing that matters is the ratio. They are all the same in practice with the exception of the total starter yield at the end. As you become familiar with the rhythm of your starter, you can begin to gauge what ratios and timings allow your starter to perform optimally in terms of both conservation feeds and strengthening feeds.

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Now you may be asking, “What if I need a bunch of starter for a particularly large bake?” That’s a great question, but just remember that you can increase your total starter amount exponentially with each successive feed. If you need to build up a large amount, you can simply scale the feeds rather than discarding. Here is an example of scaling up over just 24 hours:

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HYDRATION

Now what about hydration? Since bakers percentages are based around the total amount of flour in a bread recipe, hydration percentage is expressed as the total amount of water in relation to the flour. 100% is always the total weight of flour, so a 100% hydration starter would be equal weight flour and water. That’s easy enough to calculate, but what about 80% or 120% hydration?

For the starter, hydration percentages less than 100% yield an increasingly stiffer starter as that number decreases. Conversely, hydration percentages greater than 100% yield an increasingly wetter starter as that number increases.

Now, I’m not going to go into the reasons why you might want a stiffer or wetter starter in this post, as these reasons are varied and many! What is important is to be able to calculate how. So let’s say you want to stiffen to 80% from 100% and you are beginning with 120g of starter:

That starter consists of 60g flour and 60g water, so if you add to that 60g flour, you now have 120g total flour weight in it. Now comes the math...

120 x .8 (80%) = 96

So we know we need 96g total water to make it 80% hydration. But remember, we already have 60g water so:

96 - 60 = 36

So, by adding 36g water to the starter we have decreased the hydration from 100% to 80%. You can use the same math for increasing to 120% by multiplying by 1.2 (120%) as well. Now the new total weight of starter after that feeding is:

120g (starter) + 60g (flour) + 36g (water) = 216g total weight.

You might think that’s a difficult number to work with, but this does not matter because the next time you feed, you can begin with any amount that you like. So to continue feeding at 80% hydration you could begin by taking 180g of it, knowing that 100g of that is flour and 80g of it is water. Or 90g, knowing that 50g of it is flour and 40g water. Then just add the same respective amounts of each ingredient to it to maintain the same percentage.

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BAKER'S PERCENTAGE

Once you really understand baker's percentages, you will be able to scale any recipe to any size easily. Want to bake two or three loaves instead of 1? Just double or triple the weight of each ingredient. That’s easy, but what if you want to change the weight of your loaf? You can easily scale a recipe to any weight by adjusting the flour amount and multiplying each of the other ingredient amounts by their baker’s percentage. Here’s an example:

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You can also use baker’s percentages to compare two different recipes. This is helpful if you want to see how similar/different they are in terms of relative ingredients. If all you have is weights of each ingredient, you can't easily compare them. Take a look at these two brioche recipes as an example:

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Now let’s look at the same recipes but with just the baker’s percentages:

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The baker’s percentages remove dough weight from the equation, and allow you to easily compare relative amounts of each ingredient. 

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Now let’s look at another basic dough example, going through the process of scaling the weight of each loaf down from 900g to 750g, and then calculating total weight of all ingredients to produce 12 loaves:

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In the above example, if you wanted to change your individual loaf weight from 900g to 750g, you can use baker’s percentages to figure out how much flour to use. You add up the total of all the percentages and convert it to decimal form (in this case 200% is 2.0). Then divide your loaf weight by 2 (750 / 2 = 375). So your flour weight is 375g and every other ingredient can be calculated by multiplying 375 by their respective percentages in decimal form. 

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Now let's say you want to scale up the 750g loaf to a much larger batch size. If you wanted to make a dozen of those loaves, you just figure out what that equals in terms of total dough weight, which is 12 x 750 or 9,000g. Then divide that number by your total baker's percentages in decimal form to give you your flour amount, then calculate all the other ingredients based on their baker’s percentages.

Using this kind of math for calculations is likely going to be completely foreign at first, but the more you use it, the easier it will become. And, in the long run, it will greatly simplify the work in calculating ingredient amounts for each of your bakes, and will allow you to adjust and adapt formulas with greater ease also!

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Written by: James Bridges