Learn how much a cup of sourdough starter weighs, depending on its stage: active or discard.

Successful sourdough baking depends on ratios and timing so measuring accurately is very important.

This post will explore the role of the starter, accuracy in baking, differences in starter stages, how to measure sourdough accurately with cups, and variables that impact the weight of sourdough starter.

Understanding Sourdough Starter

What is sourdough starter?

Sourdough starter is a natural yeast (or leaven) used to ferment and rise bread in place of commercial yeast.

It is cultivated in a mixture of water and flour.

Once established, the mature starter contains colonies of microbes like wild yeast and good bacteria (lactic acid bacteria and acetic acid bacteria).

The natural yeast and bacteria consume and break down the flour to create a stronger leavening agent.

They do this by creating lots of carbon dioxide bubbles which are trapped in the webs of gluten proteins that have been created during the fermentation process.

There are three stages the sourdough starter goes through: just fed or refreshed, active, and discard.

​Read more about sourdough starters in this post: What is a sourdough starter?

What are the differences between active and discard sourdough starter?

Two important stages to recognize in your starter are active and discard.

• An active starter has been refreshed or fed in the last 5 to 14 hours at room temperature (this timing varies depending on several factors that you can learn about in this post on refreshing starters) and is very bubbly. If a rubber band was placed level with the feeding, the top of your starter should be at least double the height of the rubber band height.
  • The active starter is optimal for making bread dough and has 8 signs of readiness (not just passing the “float test”) that you can learn about in this post: How to Know When your Sourdough Starter is Ready (8 signs)
• Discard sourdough starter is liquid-like with little to no bubbles. It is unfed and dormant, meaning that it needs to be refreshed to return to good health and activity.

Learn more about these stages in these posts:

• What is Sourdough Discard?
• How to Store Sourdough Discard for Starter Discard Recipes
• How do you use sourdough discard? (7 uses and video)
• Why use Sourdough Discard?

The Importance of Accurate Measurement in Baking

The Importance of Accuracy in Sourdough Baking

In sourdough baking, and in all baking, accuracy is essential for accurate and consistent results. Here are some ways that inaccurate measuring can impact your dough:

• Change in fermentation timing
• Change in flavor
• Change in dough texture (water/liquid to flour ratio)
• Change in dough strength
• Change in final bread/recipe results

Sourdough Starter Amount in Recipes

If a sourdough recipe is not followed carefully, especially the amount of starter and the amount of ingredients used, it can impact the resulting loaf of bread.

Sourdough bread uses ratios in baking which impact the fermentation timing.

If too much starter is used, it will speed up fermentation and throw off the flavor and strength of the dough.

If too little starter is used, it will slow down fermentation and change the flavor of the dough.

​See these posts to learn more about sourdough fermentation:

• How to tell when sourdough is done with bulk fermentation
• When is sourdough finished proofing? The signs and a test
• What does overproofed sourdough bread (or dough) look like?

Weight vs. Volume in Sourdough Baking

​Measuring by volume, like many of us do in the United States, has a lot of variability.

The way different people scoop flour can vary widely! So a cup of flour can have many different weights depending on how the flour was stored, how it was scooped, and how (or if) it was leveled.

Freshly poured flour or sifted flour scooped  gently and leveled off will weigh far less that one cup flour that was scooped from a settled container of flour and then packed down as it was leveled.

I advise bakers to use a digital scale made for weighing food for best results.

The scale measures the weight and is not impacted by how a person scoops or packs ingredients when measuring.

Advantages and Disadvantages of Measuring by Volume

Advantages:

• Familiar (if you are from the United States)
• Easier for kids
• Accessible since most people have measuring cups and spoons in their kitchen

Disadvantages:

• Variability
• Can impact results if not measured accurately
• More dishes to wash up
• Conversions needed when making larger batches

Measuring Sourdough Starter by Weight

​Guidelines for Measuring Sourdough Starter by Weight

​Let’s get into this!

​Here are the most important steps for measuring sourdough starter by weight:

1. Get the right tools, like a digital kitchen scale
2. Familiarize yourself with the differences between active and discard sourdough starter (this is key)
3. Place your mixing bowl on the scale, and tare it so you can accurately measure in just the amount of starter needed.
4. Find a resource for converting the weight of other ingredients like Charlotte’s Lively Kitchen Grams to Cups Calculator

Quick Reference Conversion Chart

For quick reference, here are some common conversions for sourdough baking:

• 1 cup of all-purpose flour/ bread flour = approx. 150 g flour*
• 1 cup whole wheat flour = approx. 140 g whole wheat flour*
• 1 cup of water = 237 g water
• 1 cup of starter, active = approx. 172 g active starter
• 1 cup of starter, discard = approx. 280 g discard starter

​I have a special FREE printable you can get to use as a quick reference for several different ingredients to convert from cups to grams here: Sourdough Baker’s Conversion Chart

*Note: these amounts are approximate because how the flour and starter are scooped into a cup and the state of the starter or flour impact the final weight. 

Liquid measuring tends to be more reliable when going between volume and weight measurements. So one cup water is reliably 237 grams, some people round up to 240 grams but in sourdough those extra few grams may impact the recipe.

Weighing a Cup of Active Sourdough Starter

Measuring a Cup of Active Starter

The characteristics of an active starter are lots of bubbles and volume.

This means that a cup of active starter weighs less than a cup of discard because of all the gas in the aerated structure of the bubbly starter.

One cup of active starter weighs approximated 172 grams.

Starter Considerations that May Impact Weight

The type of sourdough starter I am referencing in this post is the most common one: 100% hydration sourdough starter* made with white flour.

A 100% hydration starter is made with equal parts by weight of water and flour. How much water is used in the starter impacts the fermentation activity as well as how dense the starter is when it becomes active.

​The type of starter and the type of flour used impact the weight of the starter.

A stiff starter has a higher weight of flour compared to the water so it is typically much denser than a 100% hydration sourdough starter.

Starters made with a different flour like whole wheat flour or rye flour instead of white flour will also be denser and therefore heavier.

Read more about starter types in these posts:

• What does a 100% Hydration Sourdough Starter mean?
• Stiff Sourdough Starter vs Liquid 100% Hydration

How to Measure a Cup of Active Starter

Even the way you fill the measuring cup could impact the weight of the active starter.

The best way to fill your measuring cup is to slowly pour the active starter into the cup.

If you scoop it out with multiple spoonfuls into the measuring cup, that will disrupt the structure and cause too much gas to escape, which impacts the final weight.

Weighing a Cup of Sourdough Discard

Measuring a Cup of Sourdough Discard

Sourdough discard is thick and runny with few to no bubbles. It looks a bit like thick ranch dressing.

At this stage, the yeast and bacteria have broken down the proteins in the gluten until they are too weak to hold in the gas bubbles.

So the dense remaining starter weighs more than it did when it was active.

One cup of sourdough discard starter weighs about 280 grams.

Discard Variables that May Impact Weight

The weight of the sourdough discard may be impacted by the type of flour used, hydration level (ratio of flour to water—100% versus stiff), or the time since the last feeding process.

​Sourdough discard that is 24 hours old may still have some bubbles in it, giving it more volume to fill the measuring cup with less weight.

Conversely, sourdough discard that has been stored in the fridge for over a week will be very thick and dense, which makes it weigh more.

For recommendations on how long to store sourdough discard, see this post: How to Store Sourdough Discard for Starter Discard Recipes

Free Sourdough Guide

You can get my free Quick Start Sourdough Guide to begin learning some of the key parts of the cycle of sourdough starter.

Learn the phases, the signs of an active, how to care for a sourdough starter to keep it alive and thriving, as well as how to make your own sourdough starter.

​​

Comparing Active and Discard Starter Weights

Weight Differences Between Active Starter and Discard

A cup of active healthy sourdough starter full of bubbles weighs less than a cup of sourdough discard due to the volume taken up by the gas.

How does Active or Discard Impact Baking?

The stage of the starter has a big impact on baking for a few reasons:

• The fermentation impact: the yeast in the active starter are in a stage where they are more conducive to healthy bread rising
• Health of the starter: a starter is a living thing so one that is in the discard stage is not in optimal health with a higher amount of waste (from microorganisms dying off and their waste from the fermentation process) and a huge population of starving microorganisms that will impact the rate and quality of the fermentation
• Balanced microorganisms: in an active starter, there is a better balance of yeast to bacteria which is better for the best results in sourdough bread recipes
• Hydration differences: sourdough discard acts more like a liquid due to its unique consistency compared to active sourdough starter which impacts the hydration of the dough

When to use Active vs. Discard Starter in Baking

​Active sourdough starter is ideal for use in sourdough bread recipes, pizza recipes, and other traditional bread recipes that require a leavening agent.

Sourdough discard is used to make recipes that usually use baking soda or baking powder like pancakes, muffins, scones, cookies, “quick breads”, and others.

In discard recipes that create a sourdough discard sponge or preferment (see my favorite sourdough waffle recipe for an example) or instruct a fermentation time for the dough, you will enjoy baked goods that are more digestible, flavorful, and with a lighter texture.

Discard can sometimes be used in bread recipes with special ratios like my Easy No Knead Sourdough Bread recipe, but cannot be used as a one-for-one replacement for active starter.

Tips for Home Bakers

Tips for Home Bakers for Measuring Accurately

• Kitchen Scale: Use a digital kitchen scale for the most accurate and best results.
• Mise en Place: Get all ingredients out and ready before you begin mixing your dough.
• Tare/Zero the Scale: When weighing ingredients into a large bowl or clean container for your starter, place the container on the scale and press the tare/zero button before adding the first ingredient. Tare/zero after each ingredient to measure accurately.
• Liquids First: Add the liquids first, starting with water. If you add too much, you can pour some out. If flour is added first, you won’t be able to take out the liquid if you over-pour.
• Pre-Measure Starter: If you are concerned you might not have enough starter for a recipe, use a separate mixing bowl to weigh out the grams of starter needed.
• Fresh Flour vs. Settled Flour: If you have flour that is older or has settled, give it a stir before measuring by cup (not needed for weight measuring). For fresh flour, like freshly milled flour, it tends to be very airy to improve accuracy for cup measuring, shake the bowl or container it is in before measuring by cup.
• Proper Cup Measuring: Don’t pack ingredients unless a recipe specifically asks you to especially when measuring flour. Pour starter when measuring for accurate results. See more details below.

Common Mistakes to Avoid When Measuring by Cups

Here are some mistakes to avoid for best results when using volume or cup measurements:

• Avoid overpacking the measuring cup.
• To measure flour, scoop and level by scraping a butter knife over the top of the measuring cup to scrape off the excess without packing.
• When measuring active starter by using a cup, pour the active starter into the cup. Scooping out spoonful by spoonful compresses the active starter which impacts the accuracy of the measurement.
• Don’t rush measuring your starter because every time it is scooped, poured, or agitated, it compresses more and impacts accurate cup measuring.

FAQs and Troubleshooting for Measuring Sourdough Starter

• How does the hydration level affect the weight of sourdough starter?
  • The hydration level of your starter (the ratio of water to flour) can affect its weight. A 100% hydration starter (equal parts water and flour by weight) is the focus of this post, which weighs around 170 grams per cup. A stiff starter with a lower hydration will be denser and weigh more.
• Why does the weight of my sourdough starter vary?
  • Variations in weight can occur due to differences in hydration levels, air bubbles within the starter, starter activity level, and slight differences in flour density.
• Can I convert weight measurements to volume measurements for sourdough starter?
  • While volume measurements can be used, weight measurements are more accurate due to the variability in density and hydration levels. Converting weight to volume is less reliable.
• How does temperature affect the weight of my sourdough starter?
  • Temperature generally doesn’t affect the weight of the starter significantly, but it can impact the volume due to gas expansion from fermentation. Warm temperatures will make your starter become active faster while cooler temperatures will slow it down.
• Is there a difference in weight between different types of flour starters (e.g., rye, whole wheat, all-purpose)?
  • Yes, different types of flour can slightly affect the weight due to their varying densities and how they absorb water.
• Why is it important to know the weight of a cup of sourdough starter?
  • Accurate measurements are crucial for consistent baking results. This helps for when you come across a sourdough recipe that uses cup measurements.
• What if I don’t have a scale?
  • If you don’t have a scale, use a conversion chart like the one I’ve created or searching online for cup to gram conversions for each ingredient. Use dry measuring cups to measure your starter.

Set up for Success

In this post, I reviewed what a sourdough starter is, volume vs. weight measurements, the importance of accuracy in baking, how much sourdough starters typically weigh and variables that impact the weight.

One cup of bubbly active sourdough starter weighs about 172 grams and one cup of liquid-like sourdough discard weighs about 280 grams.

For best accuracy and to remove these variables, use a kitchen scale to measure your starter and other ingredients.

I want you to be successful in your sourdough scaling! I invite you to explore the resources below or more posts on common FAQs here: Sourdough Troubleshooting

Equip Your Kitchen: Top Tools for Sourdough Baking

​Here are some of my favorite sourdough tools:

• Digital kitchen scale
• Spurtle for stirring your starter
• Rounded plastic dough scraper
• Round banneton or proofing bowl
• Disposable shower caps for covering bowls of dough
• Bread lame for scoring dough before baking
• Plastic cambro for storing dough and gauging bulk fermentation

Dive Deeper: Essential Sourdough Resources

I am passionate about teaching and helping you feel confident in your sourdough baking.

​Take some time to check out more of my resources on my site to grow your knowledge and find some delicious recipes in the process!

Here are a few articles you won’t want to miss:

• How to Make a Big Batch of Sourdough Bread (Calculator)
• How to tell when sourdough is done with bulk fermentation
• When is sourdough finished proofing? The signs and a test
• How to Know When your Sourdough Starter is Ready (8 signs)
• What does overproofed sourdough bread (or dough) look like?
• How to Shape a Sourdough Sandwich Loaf and Bake with Steam
• How to Freeze Sourdough Bread, Scones, & More (Easy & Fast)
• Is my sourdough starter dead?

And I would love to hear if this article has been helpful or if you have any questions! Comment down below to connect!

Just getting started with sourdough?

A competent guide transforms sourdough baking from overwhelming to uncomplicated and fun!

Get My Free Quick Start Sourdough Guide: Learn the key terms and concepts in sourdough baking, including the differences between active sourdough starter and sourdough discard, and how to care for your starter.

Time Planning Help for Sourdough Baking

The #1 need for sourdough bakers is help with time planning, so I created a resource for you.

Sourdough Time Planning Workbook: Perfect for new or experienced bakers, this workbook includes 8 templates ready to fill in and a baking journal. The templates cover 4 different ways to make classic sourdough country breads, 3 time planning worksheets for enriched sourdough bread depending on serving time target, and a blank template. The baking journal goes over baker’s percentages and how to take notes on your sourdough bakes.

Get a free sample of the workbook: Use this sourdough time planning worksheet sample to simplify your baking.

This post contains affiliate links. Read my policy here.​