312 area code — Chicago, IL geographic

Data: NANPA public reports, current as of July 28, 2026.

312 is the area code for Chicago, Illinois, in service since January 1, 1947, Central time. Together with 872 it forms the 312/872 overlay. Because of number portability and VoIP, the area code tells you where the number was issued, not where the caller is right now.

NANPA lists 785 active NXX prefixes in 312, assigned to 37 carriers. 413 of those prefixes are pooled — shared between carriers in thousands-number blocks. The code spans 8 rate centers (billing localities).

To check where a specific 312 number was issued, look up its six-digit prefix; to check who is actually calling, ignore the display and verify through an official callback number — caller ID is assertable and routinely spoofed.

The dialing plan is 1+10D for home-NPA local calls and 1+10D across codes.

Official projections put exhaust for the 312/872 complex at 1Q 2049.

Later relief produced 708 (1989), 773 (1996), 872 (2009) from its territory.

Largest localities in 312

FAQ

Where is a 312 number from?

312 is assigned to Chicago and surrounding areas of Illinois in the Central time zone. The three digits after the area code (the prefix) narrow it down to a rate center.

Is 312 a toll-free number?

No. 312 is a geographic code; calls are billed like any other domestic call. Toll-free codes are 800, 833, 844, 855, 866, 877 and 888.

Why do 872 and 312 cover the same place?

They are overlays: when a code runs low on numbers, a new code is added over the same territory instead of splitting it. The 312/872 complex shares one service area, and local calls are dialed with 10 digits.

Will 312 run out of numbers?

NANPA's current forecast projects exhaust in 1Q 2049 — decades of capacity remain.