New York City Has Been Estimated to Have 3 Million Rats. But How Was That Number Calculated?

New York City has long been associated with rats, but one number has attracted particular attention: an estimated population of about 3 million rats.

The figure sounds precise, especially when it is repeated online as though scientists counted every rat across the city's five boroughs. They did not.

The 3-million figure is a statistical estimate based on publicly available rat-sighting data and a model used to estimate the number of rat-inhabited lots. It provides an indication of the possible scale of New York City's rat population, but it is not a literal census of individual animals.

Brown rats foraging near discarded food and garbage on an urban New York City street. Illustration: The Pader.

Where Did the 3 Million Rat Estimate Come From?

The widely repeated estimate traces back to statistical work using rat sightings reported to New York City's 311 system.

In earlier research, statistician Jonathan Auerbach used publicly available 311 rat-sighting reports from 2010 and 2011 as a proxy for a capture-recapture approach. This type of statistical method can be used to estimate animal populations when researchers cannot directly count every individual.

A later analysis by M&M Pest Control applied a similar methodology to more recent data from 2022 and 2023. The analysis estimated that New York City could have as many as 3 million rats.

The important phrase is "as many as." The number is an estimate produced from a model, not a direct count.

How Can Anyone Estimate Millions of Rats?

Counting every rat in a city as large and densely populated as New York would be extremely difficult. Rats are mobile, often hidden, and can live in places that are difficult for people to inspect.

Instead of attempting to find every individual animal, researchers can use information about where rats are being reported and how those observations relate to the distribution of potentially rat-inhabited locations.

In the 2023 analysis, M&M Pest Control reported an estimated 59,384 rat-inhabited lots in 2022. The analysis then used an assumption that each such lot could support up to 50 rats, producing an estimate of roughly 3 million animals, with an uncertainty of about 100,000.

That assumption is important. Changing the assumptions used in a statistical model can change the resulting estimate.

So Is There Really One Rat for Every Three New Yorkers?

That comparison comes from putting the estimated 3 million rats next to New York City's human population.

The U.S. Census Bureau's 2025 population estimate puts New York City's population at approximately 8.58 million. If the 3-million-rat estimate were used for comparison, that would be roughly one estimated rat for every 2.9 people.

That is why the viral statement is often simplified to about one rat for every three people.

But this comparison should not be interpreted as proof that scientists know the exact number of rats living in the city. Both the rat figure and the human population figure have different statistical foundations, and the rat figure is specifically an estimate rather than a census.

The Rat Population Is Not Necessarily Staying at 3 Million

Another reason the viral claim needs context is that rat populations can change over time.

New York City's Department of Sanitation reported that rat sightings submitted through 311 declined for 12 consecutive months through November 2025. From December 2023 through November 2024, residents reported 25,230 rat sightings. During the same period one year later, the number was 20,025, a decline of 20.6 percent.

The city linked the decline with changes in how trash is stored and collected, including requirements for more garbage to be placed in sealed containers.

A reduction in reported sightings does not automatically prove an equivalent percentage reduction in the total rat population. Sightings are a measure of reported activity, not a direct population census. However, they are an important indicator that researchers and city agencies can track over time.

New York City Has Continued Tracking Rat Activity

The city's efforts to reduce rat activity have continued beyond the period covered by the original 3-million estimate.

In April 2026, New York City reported that rat sightings had fallen by about 30 percent in the context of its broader sanitation and rodent-mitigation efforts.

The city has also expanded its use of trash containers and other measures intended to reduce rats' access to food and places where they can establish colonies.

These developments are another reason the 3-million figure should be treated as a historical statistical estimate rather than a permanent population count.

Why Are Rats So Successful in New York City?

Rats are highly adaptable mammals. Urban environments can provide many of the things they need to survive, including food, water, shelter and protected spaces for nesting.

Discarded food and accessible garbage can provide an especially important source of nutrition. Buildings, underground infrastructure, parks, vacant spaces and other structures can also provide opportunities for shelter.

New York City's own health guidance emphasizes the importance of reducing accessible food and improving sanitation to make environments less suitable for rats.

This helps explain why waste management is such an important part of urban rodent control.

Are the 3 Million Rats Mostly Brown Rats?

The rats commonly associated with New York City's urban environment are brown rats, also known as Norway rats, scientifically called Rattus norvegicus.

They are well adapted to human-dominated environments and can live around buildings, streets, parks, garbage areas and underground spaces.

However, the 3-million estimate should not be interpreted as a precise species census. The statistical analysis was designed to estimate the city's rat population rather than produce an exact count of every individual animal.

What the 3 Million Figure Really Tells Us

The most useful lesson from the estimate is not that New York has exactly 3 million rats. It is that urban wildlife populations can be extremely difficult to measure.

Scientists and pest-management researchers often have to work with indirect evidence when animals are difficult to observe. Sightings, reports, surveys and statistical models can provide useful estimates, but the results need to be interpreted according to the methods and assumptions behind them.

In New York City's case, the 3-million estimate helped illustrate the possible scale of the city's rat problem. More recent 311 data provides another way to track how visible rat activity has changed over time.

FAST FACTS

Conclusion

New York City's often-repeated figure of 3 million rats has a real statistical basis, but it is easy to misunderstand.

The number was not produced by counting three million individual rats. It came from a statistical analysis using rat-sighting data and assumptions about the number of rats that could occupy affected lots.

That makes the viral claim reasonable as a description of an estimate, but misleading if presented as an exact population count.

And because New York City's reported rat sightings have changed substantially in recent years, the 3-million figure should be viewed as an estimate from a particular period—not a permanent count of every rat currently living in the city.

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