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US area code · Illinois

Area code 312

Where the 312 area code is, its overlay and how to dial a +1 312 number from anywhere.

CoversChicago, IllinoisTime zoneCentral (CT)TypeOverlay
Quick answer

The 312 area code is in Chicago, Illinois, United States (Central (CT)). To call from abroad: +1 312 555-0123. It is an overlay, so all 10 digits are dialled.

StateIllinois
Main areaChicago
Time zoneCentral (CT)
TypeOverlay
10-digit dialingRequired
In service since01-Jan-1947

The 312 area code is a geographic North American Numbering Plan (NANP) code covering Chicago, Illinois. It has been in service since 01-Jan-1947 and sits in the Central (CT) time zone.

Overlay 312 shares its region

Several area codes cover the same geographic area, so two neighbours can have different codes. Because of the overlay, you must dial all 10 digits (area code + number) even for local calls.

312872

How to dial a 312 number

From abroad+1 312 555-0123
Within the US / Canada1 312 555-0123
Locally (same area)312 555-0123

Cities in the 312 area code

A 312 number is usually in one of these places in Illinois — 1 county.

West Chicago Dupage

Other Illinois area codes

217224309331447464618630708730773779815847861872

Frequently asked questions

Where is the 312 area code?

The 312 area code is in Chicago, Illinois, United States (Central (CT)).

Is 312 an overlay area code?

Yes. 312 overlays the same region as 872, so callers dial all 10 digits.

Do I have to dial 10 digits for 312?

Yes — dial the area code plus the seven-digit number.

How do I call a 312 number from another country?

Dial your exit code (or +), then 1, then 312, then the number: +1 312 555-0123.

Source: NANPA numbering plan. An area code covers a region, not a precise address — a 312 number does not pinpoint a street or ZIP code.

Missed a call from +1 312?

In the 30 days to September 24, 2026, 385 unwanted calls showing a 312 number were reported to the US Federal Trade Commission, 46% of them recorded messages or robocalls. That puts 312 at #253 of 670 area codes reported.

Other184
Dropped call or no message65
Reducing your debt (credit cards, mortgage, student loans)36
Calls pretending to be government, businesses, or family and friends27
Before you call back
  • If you do not know anyone in Illinois, do not call back: a genuine caller will leave a message or send a text.
  • Scammers fake the number shown on caller ID, so a 312 number can hide a caller anywhere in the world.
  • Never give a code received by text or a bank detail to an unknown caller. In the US, calls can be reported at reportfraud.ftc.gov.

Who issues +1 312 numbers

Phone companies hold blocks of numbers in each area code. The main holders in 312:

Illinois Bell Tel Co 334New Cingular Wireless PCS, LLC 82T-Mobile USA, Inc. 64Cellco Partnership Dba Verizon Wireless 54Mcimetro Access Transmission Services LLC 33Spok, Inc. 33

About 25.2% of the 798 prefixes in use belong to mobile carriers: a 312 number is often a cell phone, and it may have moved to another carrier since.

Sources: FTC Do Not Call reported calls (numbers as reported by consumers, not verified), NANPA central office code assignments.

All US area codes United States +1 Map of area code 312 — cities & rate centres