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312 Area Code

Area code 312 serves Chicago, Buffalo Grove, Wheeling and Prospect Heights in Illinois. It has been in service since January 1, 1947.

StateIllinois
Time zoneCentral
Local time now…
Prefixes in use784
Overlay with872
Projected to run out2049
ChicagoBuffalo GroveWheelingProspect HeightsChicagoBuffalo Grove
Cities and towns served by area code 312

Who issues 312 numbers

Mobile 26%VoIP and cable 19%Landline 56%

Share of the 784 prefixes (the three digits after 312) assigned to each type of carrier. Classification by carrier name, approximate.

CarrierPrefixes
AT&T (Illinois Bell)334
AT&T Mobility82
T-Mobile64
Verizon Wireless54
Verizon Business (MCImetro)40
Lumen (Level 3)34
Spok33
Onvoy (Sinch)23

Cities and towns in area code 312

CityPopulationOther area codes
Chicago2,731,585773, 872
Buffalo Grove42,812847, 224
Wheeling38,391847, 224
Prospect Heights15,552847, 224

Got a call from 312?

A 312 number was originally issued in Illinois, but that does not prove the caller is there. 19% of 312 prefixes belong to VoIP and cable providers, whose numbers can be bought online and used from anywhere. Caller ID can also be spoofed, so treat urgent requests for money, codes or passwords from any area code with suspicion, and call back on a number you already know.

All 784 prefixes in area code 312

Format: (312) XXX-YYYY. Carrier is the company the block was originally assigned to; numbers may since have been ported to another carrier.

Questions about area code 312

Where is area code 312?
Area code 312 is in Illinois. It covers Chicago, Buffalo Grove, Wheeling and Prospect Heights.
What time zone is area code 312?
Area code 312 is in the Central time zone.
Is 312 a toll-free number?
No. 312 is a geographic area code in Illinois. Toll-free numbers in the US start with 800, 833, 844, 855, 866, 877 or 888.
Why does 312 share its area with 872?
312 and 872 form an overlay: they cover the same territory, so new numbers there can get any of these codes, and local calls need all 10 digits.
Will area code 312 run out of numbers?
NANPA's latest forecast projects the 312/872 overlay to exhaust in the first quarter of 2049. Before that happens, a new area code is usually added as an overlay; existing numbers keep their code.

Other area codes in Illinois