Why You Should Always Feed Your Sourdough Starter in Grams – Never in Cups

If you've ever embarked on the journey of keeping a sourdough starter, you know it can be both a rewarding and temperamental process. The secret to a healthy, bubbly, and strong sourdough starter lies in not only consistency but also in food amounts. However, a common mistake many sourdough bakers make is feeding their starter using volume measurements like cups, instead of weighing ingredients in grams. Here’s why feeding your starter using cups can lead to disaster—and why using grams is essential.

1. Flour and Water Don’t Weigh the Same

At the heart of feeding your sourdough starter is the balance between flour and water. For a typical feeding ratio like 1:1:1 (starter: water: flour), the weight of the water and flour is crucial to maintaining the right consistency.

Why does this matter?
Water weighs more than flour. When you use cups to measure, 1 cup of water will weigh significantly more, while 1 cup of flour will weigh less (though this can vary). If you're feeding by volume (cups), the water-to-flour ratio is thrown off. Your mixture will end up being too wet, which means your starter will be overhydrated and not fed enough flour. This imbalance leads to a starter that lacks structure and isn't able to grow as robustly.

In contrast, feeding by weight ensures you're adding exactly equal parts water and flour, which helps maintain the proper balance for your sourdough starter to thrive.

2. Inconsistency in Flour Measurement

Measuring flour by cups is notoriously inaccurate. Depending on how you scoop, your cup of flour, it could weigh anywhere from 90 to 150 grams, based on a variety of factors:

• Compaction: Scooping flour can compact it, making the same cup hold more or less depending on how much pressure was applied.
• Air content: If you fluff your flour beforehand, your cup measurement could be lighter than a densely packed cup.
• Flour type: Whole grain flour is denser than white flour, leading to variations in the amount you're feeding your starter.

The problem here is that your sourdough starter is highly sensitive to these differences. Feeding it too little flour can result in it being underfed, and if this happens regularly, your starter won't be able to develop properly. You may notice a starter that smells like vinegar or acetone—signs that it's hungry and has been fermenting too long without enough food (flour).  It's a telltale sign your starter isn't being fed properly.

By weighing your flour in grams, you eliminate these variables. Whether you’re using all-purpose, whole wheat, or rye flour, your starter will get a consistent, balanced feed every time.

3. Risk of Underfeeding Your Starter

Using cups almost always results in underfeeding your starter. As mentioned earlier, since water weighs more than flour, if you feed your starter based on volume, you are likely adding too much water and not enough flour. The issue with this is that sourdough starters need adequate food (flour) to maintain a healthy yeast and bacteria population. If there's not enough flour in the mix, your starter will start to starve.

Signs of an underfed starter:

• Unpleasant smell: A starter that hasn’t been properly fed often takes on a sour, sharp smell, like vinegar or even acetone (nail polish remover). This happens because the natural yeasts and bacteria in your starter are breaking down the flour too quickly and then resorting to consuming the waste byproducts of fermentation, leading to an overgrowth of acetic acid.
• Sluggish rise: An underfed starter won’t rise as quickly or as high as it should after feeding. This can make it difficult to use when baking bread, as it will lack the strength needed for a good dough rise.
• Inconsistent texture: Your starter may look watery or separate into layers of liquid and dough, indicating that it is off balance and not being properly nourished.

Weighing your ingredients ensures that your starter gets the right amount of flour every time, preventing these issues and keeping it healthy.

4. Precision Matters in Sourdough Baking

Sourdough baking is all about fermentation, and fermentation is a science that thrives on precision. While many other recipes allow for some flexibility in measurements, sourdough starters are much less forgiving.

Feeding ratios like 1:1:1 (starter:water:flour) or 1:2:2 are not just guidelines—they're essential formulas to keep the microbial balance of your starter in check. Using grams allows you to be exact and reliable in every feed, ensuring your starter has the correct hydration level and enough food to stay strong.

How to Switch to Feeding in Grams

If you're ready to make the switch to feeding your sourdough starter in grams, it's a straightforward process. You'll need a kitchen scale, which allows you to weigh your starter, water, and flour with ease. Here’s how you can do it:

1. Weigh your starter: If you're maintaining a 1:1:1 feeding ratio, weigh the amount of starter you’re feeding (the amount of starter that is in the jar), and use that weight as your guide for how much water and flour to add. For example, if your starter weighs 50 grams, you'll add 50 grams of water and 50 grams of flour.  A helpful tip is the know how much your jar weighs empty and clean without the lid on and subtract the weights.

2. Weigh your flour: Place a bowl on the scale, zero it out, and weigh the exact amount of flour. This ensures you’re adding the correct amount, regardless of how compacted or fluffy the flour might be.

3. Weigh your water: Weigh your water to match the weight of your flour for a 1:1 ratio. If using a different feeding ratio like 1:2:2, you would double the amount of flour and water based on the weight of your starter.

By making this small change, you’ll see a big difference in the health, strength, and consistency of your sourdough starter.

5. Cups Aren’t Standardized Worldwide, But Grams Are

Another important reason to avoid feeding your sourdough starter using cups is that cup measurements aren’t standardized globally. In the U.S., 1 cup of water equals 240 milliliters, while in the U.K. or Australia, it’s 250 milliliters. This difference might seem small, but it can lead to discrepancies when feeding your starter, resulting in inconsistent hydration and feeding ratios. Additionally, cups can vary in size, shape, and accuracy depending on the brand or country, making it even harder to maintain precision. Grams, however, are a universal unit of measurement that remain the same no matter where you are. Using grams ensures that no matter what type of flour or water you're using, you’ll always be feeding your sourdough starter with the exact right amount, keeping it consistent and reliable.

6. Why the "Eyeballing Method" Doesn’t Work when Feeding Sourdough Starters

Some bakers may rely on the "eyeballing method" to feed their sourdough starter, estimating amounts of flour and water without precise measurements. While this might work for a short time, it almost always leads to problems in the long run. Sourdough starters rely on a delicate balance between yeast and bacteria, which thrive when the starter is fed accurately. Guessing amounts can cause inconsistent feeding, resulting in a starter that's either too wet or too dry. Over time, this inconsistency weakens the starter, making it sluggish, acidic, and less likely to rise properly. The natural fermentation process needs precision to stay balanced—"eyeballing" simply can’t provide the accuracy required to keep your starter healthy and active. By measuring in grams, you ensure every feeding is consistent, helping your starter stay strong and predictable.

Accuracy Equals Success

In sourdough baking, precision is key. Using grams to feed your starter ensures consistency, eliminates variables like compacted flour, and guarantees your starter is getting exactly what it needs. When you measure by weight, you’re giving your sourdough the best chance to thrive, leading to better flavor, rise, and overall success in your bread baking.

So, ditch the cups and grab a scale—your sourdough starter will thank you!