How Many Composting Worms Do You Need?

  • By: Sam Richards
  • Date: October 23, 2020
  • Time to read: 6 min.

Worm composting has long been a popular method for providing soil the with the nutrients necessary for the health of plants. Through their castings, worms excrete organic matter that will fortify the ground and provide the valuable amendments that will help plants to thrive.

While many things will be influential in the success of vermicomposting, one of the most important would be the worms you will use. With this, many of you are most probably curious – how many worms do I need? There’s no easy way to answer this question as this will depend on several variables. Read on and learn from some of the insights we’ll be sharing in this short guide.

How Many Composting Worms Do I Need?

It depends – that is perhaps the best way to answer the question regarding the composting worms that you will need. Generally, two main factors will affect our answer to this question:

  • The size of the bin or the available space
  • The food waste that you are producing at home

Once you know the two things mentioned above, it will now be easier for you to determine the amount of the composting worms that will be necessary for your bin. Below, we’ll take a closer look at these things.

Based on the Size of Your Bin

One of the best things to do is to start with the size of your bin. It is one of the easiest indicators of how many worms will be needed for composting. One good rule of thumb to follow is to use one pound of worms for every square foot in your composting bin. For instance, if you have two square feet bin, then you will need two pounds of worms.

However, two main things should be noted with the assumption above:

  • Red worms can multiply quickly, especially when you make sure that they are living in a healthy environment. You must transfer the worms in another bin to prevent having more than what is necessary.
  • The bigger the bin and the more worms are present, the more food scraps there should be. Make sure that you can meet the feeding requirements of the worms. Otherwise, you should settle with a smaller bin.

Based on the Food Waste You Produce

Aside from the size of the bin, another important consideration would be the food waste that you are producing at home. The more food scraps you have, the more worms there should be in your composting bin.

It is difficult to estimate the food scraps that you are making in one week. The best thing that you can do is to collect all the scraps and put them in a plastic bag. Weigh the food scraps. In a one to two-person home, you will have an average of four pounds in a week. For larger households, the food scraps can be eight to ten pounds in a week.

Once you know the amount of food waste that you are generating in the household, you can identify how many worms you will need to have in your composting bin. Here are some of the most important things to note.

  • Most worms, especially red wigglers, can eat half of their body weight in a day.
  • If your average food waste is two pounds in a day, then you will need at least four pounds of composting worms in your bin.

How Many Worms are in One Pound?

In the case of most sellers, you will see that they are selling worms by the pound. You won’t have the chance to count how many worms are in a pound. Even if you have the opportunity, you will most likely not go through the hassle of doing so. Below are some of the most important things to keep in mind:

  • A one-pound bag of composting worms will be roughly equivalent to two cups.
  • Some bags of work will not have uniform-sized worms. They will be in all stages of their life. Some will be cocoons while others will be fully developed.
  • On average, there will be 1,000 mature worms in one pound or two cups.
  • For juvenile worms, one pound will have about 4,000 worms.
  • There can be as much as 100,000 hatching worms in one pound!

Can You Have Too Many Worms?

This is another question that raises the curiosity of many beginners in worm composting. It can be bad for your plants and worms themselves.

  • Having too many worms means that there will be too little room for them to wiggle. This can affect their quality of life.
  • Worms will end up fighting over limited food scraps when their population is more than what your composting needs.
  • They will also disrupt the bacteria in the bin. They will be eating almost anything, and hence, when they are crowded, you might also end up having limited beneficial bacteria.
  • If you think that your composting bin has more worms than what is necessary, the best thing that you can do is to move some of these worms in a new bin.

What Size of Bin is Needed?

Aside from the number of worms, the right size of the composting bin is also a crucial consideration. Here are some of the things to keep in mind:

  • It is recommended to have one pound of worms for every square foot of your composting bin. This means that if the bin is four square feet, then you will also need four pounds of worms.
  • Take note that under ideal environments, such as with the right temperature and proper feeding, worms can grow big quickly. So, consider how big they will grow, and make sure that there’s enough space in the bin for their population.

How Many Composting Worms Should You Start With?

If you are a beginner, it is best to start with 250 to 500 worms in a small bin. Start small and grow your worms before going full-blown. When you are starting, you still have a lot of things to learn, and hence, you should be more cautious.

You should not buy thousands of worms, especially when you are on a budget. To save money, consider growing your worms. Start with a bag that contains 500 worms. Feed them based o their nutritional requirements, and eventually, they will reproduce. This way, you will have more worms out of the original number you have. The best thing is that you won’t need to buy more worms!

Picking the Right Bin

Much has been said about how many worms are needed in a compost. However, one more thing that you should know is the type of bin to use. Below are some pointers when it comes to bin selection:

  • Make sure that there are sufficient air holes. They will help in the aeration of the soil. When the soil is properly ventilated, it will be healthier, which will provide an ideal environment for the worms to grow.
  • Choose plastic. This is an affordable and lightweight material.
  • Avoid metal. It can be prone to rust, especially when it is outdoors.
  • Wood is also a bad choice. It can be easily prone to decay, especially when exposed to the rain and sun.
  • You do not need bins that are too deep. Worms will live and eat on the top six to eight inches of the soil.

Avoid Overfeeding Your Worms

Now that we have talked about how many worms you need in your compost, let’s talk about how you can feed them. They will eat fruits and vegetables, as well as paper, eggshells, and coffee grounds. Do not give them anything spicy. You should also avoid meat and processed food. The most important is that you do not overfeed the worms. Otherwise, here are some things that can happen.

  • The soil can become too acidic, increasing the chances that the worms will die.
  • There will be limited space for the worms to move around.
  • Food will rot when supply is too much. In turn, this can produce a foul odor.
  • Pests and unwanted critters can be present in your composting bin.
  • Excess food scrap will create excess moisture, which will make the soil damp.


At this point, we hope that we have already answered your question about how many worms are needed in a compost. In short, this will depend on two things – the size of the bin and the amount of food waste that you are making at home.

On average, you will need about one pound of worms for every square foot of space in your bin. More so, based on your food scraps, take note that worms can eat half of their body weight. So, if you have two square feet of bin, you will need two pounds of worms. More so, if you have two pounds of waste, then you will need four pounds of worms.

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