HomeAnimal WelfareHow many animals are factory-farmed?

How many animals are factory-farmed?

The majority of farm animals in the world are factory-farmed.

More than 100 billion animals are killed for meat and other animal products every year.1 That’s hundreds of millions of animals every day.

This in itself amounts to a large amount of animal suffering. But what also matters for animal suffering is what their lives are like up to the moment they are slaughtered: did they live in discomfort and poor conditions, or did they have a relatively pain-free life?

It’s difficult to capture animal living conditions with a single metric, but one indicator that is often used is whether animals were raised in ‘factory farms’.

In this article, I first define factory farms and then ask how many animals are raised in these conditions. I first focus on the United States, where we can get fairly good estimates from national statistics. Then, I look at some global estimates, which are much lower quality but might give us a sense of magnitude for these numbers.

What are factory farms?

There is no specific definition of a ‘factory farm’.

In agricultural research, they are often known as ‘concentrated animal feeding operations (CAFO)’.

The US Department for Agriculture has consistent criteria for CAFOs to track and quantify these farms. An animal feeding operation (AFO) is an operation where animals are kept and raised in confined situations. The animals are confined for 45 days or more in a 12-month period. In other words, they have no access to the outdoors over this period.

A concentrated animal feeding operation then has to meet a threshold for the number of animals confined in that space. This matters for their living conditions and the density of animals.

It defines it as an intensive feeding operation where many animals are confined for over 45 days a year. The USDA also has criteria based on how wastewater from the farm is treated and handled.

The threshold for a ‘large number’ is based on the type of animal – size matters. The number is much larger for chickens than it is for cows.

For example, an operation home to between 300 and 999 cows is defined as a ‘medium-sized CAFO’, but a medium-sized chicken farm needs to have between 37,500 and 124,999 animals.

What’s curious about these definitions is that there is no measurement of the size of the operation that these animals are held in. That obviously also matters for their well-being. It matters whether a barn holding 500 cows is 500, 1000, or 2000 square meters.

This additional measure to calculate the density of animals seems important to their level of discomfort in factory farms. Data on this would be very valuable. However, it’s unlikely that the variation in density varies significantly amongst most large farms. While there may be some farms that meet the criteria for CAFO but are large enough to give animals lots of space, this number is likely to be small.

Most CAFOs – or factory farms – will have animals in cramped and uncomfortable conditions, not only in terms of the small space given to them but also their restrictions from outdoor conditions that allow them to perform natural behaviors. Smaller animals, such as chickens, also tend to be treated more poorly and packed more tightly relative to their body size, in addition to fitting many animals on each farm.

Nearly all livestock animals in the US are factory-farmed

There is, unfortunately, no regularly updated data source that tracks farming conditions and the number of animals that are factory farmed.

However, the Sentience Institute has used publicly available data – in this case, published by the USDA Census of Agriculture (number of animals per farm) and Environment Protection Agency (CAFO definitions) – to estimate the extent of factory farming in the US.

It makes its data and calculations transparent for others to see how they arrive at these figures.

It estimates that 99% of livestock in the US were factory-farmed in 2017.2 That was 10 billion animals. More than the global human population.

This share varied by the type of animal.

All fish raised in fish farms were considered to be factory-farmed. More than 98% of chickens, turkeys, and pigs were. Cows were a bit more likely to be raised outside in fields, with greater space and freedom. Nonetheless, 70% were still fed in concentrated feeding operations for at least 45 days a year.

In the chart, I’ve shown the number of each animal raised on factory farms.

Schematic of the number of farm animals in the US that are factory-farmed. The number of factory-farmed and not factory-farmed are given for chickens, farmed fish, hens, pigs and cows.

What do global estimates tell us?

Global figures are even harder to find.

The Sentience Institute has also tried to estimate these numbers based on the best available data. But it warns that they come with significant uncertainty.3

With that warning, let’s see what the figures suggest. We’ll start with land animals because the uncertainty for fish is highest.

It’s estimated that three-quarters – 74% – of land livestock are factory-farmed. That means that at any given time, around 23 billion animals are on these farms.

The total in any given year would be several times as many. For example, we know that around 70 billion chickens are slaughtered each year. More than three-quarters of those chickens will be factory-farmed (since chickens are most likely to be farmed intensively). Let’s say 90% are. That comes to more than 60 billion per year alone, without considering any other animals.4

Assuming that most fishing farming is done under factory farm conditions, 111 billion more animals are factory-farmed. 111 billion is the central estimate from the Sentience Institute; this has wide uncertainty, ranging from 39 to 216 billion. For context, that’s about the same as the number of humans that have ever lived (estimated to be 108 billion).

Combine land animals and fish, and the final estimate comes to 94% of livestock living on factory farms.

We can do a sense check on these numbers by comparing them to the US. I would have expected that, globally, a lower share of land animals would be factory-farmed than in the US. This is for two reasons. First, the US farms many chickens, and these animals are most likely to be factory-farmed. Second, the US factory farms are particularly efficient (but intensive) in producing as much meat as possible. Other countries will have less intensive systems.

The share of global land-based livestock that lives in factory farms is probably less than in the US. Three-quarters globally seem, therefore, like a reasonable estimate.

However, the difference between the global and US figures would likely be smaller when we include fish. This is because nearly all farmed fish are raised in intensive conditions, and the rest of the world produces much more aquaculture than the US. Most of the world’s fish farms are in Asia.

When we include fish, the share of livestock raised in factory farms increases significantly, closing the gap between the global and US totals.

Taken together, we are in a situation where we have relatively little good data. However, the evidence we do have suggests that more farm animals in the world live on factory farms.


I would like to thank Jacy Reese Anthis, Max Roser, Pablo Rosado, and Edouard Mathieu for their valuable feedback and suggestions on this article.


  1. Over 75 billion animals on land are slaughtered every year for meat. Data on the number of fish killed every year is highly uncertain. When we include best estimates for farmed fish, this figure more than doubles. The Sentience Institute has a mid-point estimate of the number of farmed fish of 111 billion. If wild fish catches are included, this number is much higher.

  2. The USDA has not yet published a more recent agricultural census, which is released every 5 years.

  3. There are two main reasons for this uncertainty. The first is that it takes some assumptions from the WorldWatch Institute, which does not document its methodology clearly. The second is that global estimates of the number of farmed fish are difficult to find. As we cover in our work on Fish and Overfishing, these numbers are presented in tonnes or kilograms of seafood, not the number of animals. This point makes clear how little attention is given to animal welfare issues: animals are discussed in terms of tonnage of meat, not as individuals.

  4. While chickens can live for many years in the wild, most are slaughtered within two months in factory farms.

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    author = {Hannah Ritchie},
    title = {How many animals are factory-farmed?},
    journal = {Our World in Data},
    year = {2023},
    note = {}
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