How many illegal aliens are in the US as of December 31, 2025
Executive summary
No single, authoritative tally exists for how many people were living in the United States without legal status on December 31, 2025; independent researchers and advocacy groups produce divergent estimates that reflect different data sources and methods. Contemporary reporting and academic work place the likely figure somewhere between roughly 11 million and 15 million, with an outlier estimate of 18.6 million from the Federation for American Immigration Reform (FAIR) that rests on different assumptions and has been disputed by mainstream demographers [1] [2] [3].
1. The basic problem: no one number, many methods
Counting unauthorized residents is a statistical exercise, not a head count, because household surveys, administrative entries, parole releases, and enforcement records each capture different slices of the population and miss others; methodologists therefore produce residual estimates, administrative tallies, and model-based projections that can differ substantially [4] [5].
2. Where mainstream research clusters: roughly 11–14 million
Multiple respected research centers and academic teams converged in 2023–2025 on estimates in the low-to-mid‑teens: the Center for Migration Studies reported about 11.7–12.2 million in 2023 and related work by Migration Policy Institute and other scholars produced mid‑teens-era baselines (~13.7 million for mid‑2023 in MPI reporting), which many analysts use as the starting point for short‑term trend analysis into 2024–2025 [3] [6] [7]. Pew’s later work revised earlier series and showed the population rising to a record 14 million in 2023 in an August 2025 report and noted incomplete data for 2024–2025 that make final year‑end counts provisional [8] [9].
3. The high‑end outlier: FAIR’s 18.6 million estimate
FAIR, a long‑standing immigration‑restriction advocacy group, published a March 2025 update estimating about 18.6 million “illegal aliens,” a figure substantially above academic centers’ estimates and driven by alternative assumptions about undercount rates and recent arrivals; FAIR’s number is treated in the literature as an outlier and reflects different methodological choices rather than a consensus shift [2] [1].
4. Why estimates diverge so much in 2024–2025
Rapid policy changes, large and shifting flows at the border, the use of parole and other temporary programs, and revisions to Census Bureau net migration estimates made 2024–2025 a uniquely unstable measurement period; DHS administrative counts (releases at the border, parole entries) give timely but partial views, while survey‑based residual methods lag and can miss recent surges or declines depending on timing and sampling [9] [5] [4].
5. What a careful synthesis says about Dec. 31, 2025
Given the available sources through 2025, the defensible public‑facing answer is a range: most academic and think‑tank methods support a year‑end 2025 count in the low‑to‑mid teens (roughly 11–15 million), with FAIR’s 18.6 million as a higher outlier that highlights methodological sensitivity to undercounts and recent arrivals; no federal agency published a single definitive December 31, 2025 count that reconciles these methods [3] [6] [8] [2] [1].
6. What this uncertainty means for policy and reporting
The wide band of estimates matters: policy choices about enforcement, legalization, and resource allocation hinge on scale, and advocates on both sides selectively cite preferred estimates to bolster political arguments; readers should always check which methodology underlies any cited number because headline figures (11 million, 14 million, 18.6 million) are not interchangeable and reflect different assumptions about emigration, temporary parolees, and survey undercount [10] [8] [2].
7. Bottom line
There is no single authoritative head count for “illegal aliens” on December 31, 2025; the most credible synthesis of contemporary sources places the number in the low‑to‑mid‑teens (approximately 11–15 million), with an outlier estimate of 18.6 million from FAIR that should be treated as methodologically distinct from mainstream academic estimates [3] [6] [8] [2] [1].